Technique for performing multi-link communication in wireless communication system

ABSTRACT

According to various embodiments, a multi-link device (MLD) operating in a plurality of links can receive a PPDU through a first link from among the plurality of links. The PPU can include a first information field related to a second link that is differentiated from the first link. The first information field related to a second link can include a second information field related to a link identifier of a second link and a third information field related to whether all pieces of element information related to a second link is included in the PPDU.

BACKGROUND Field of the Disclosure

The present specification relates to a technique for performingmulti-link communication in a wireless local area network (WLAN) systemand, more particularly, to a method for transmitting information on alink in multi-link communication and an apparatus for supporting thesame.

Related Art

Wireless network technologies may include various types of wirelesslocal area networks (WLANs). The WLAN employs widely used networkingprotocols and can be used to interconnect nearby devices together. Thevarious technical features described herein may be applied to anycommunication standard, such as Wi-Fi or, more generally, any one of theIEEE 802.11 family of wireless protocols. A wireless local area network(WLAN) has been enhanced in various ways. For example, the IEEE 802.11axstandard has proposed an enhanced communication environment by usingorthogonal frequency division multiple access (OFDMA) and downlinkmulti-user multiple input multiple output (DL MU MIMO) schemes.

The present specification proposes a technical feature that can beutilized in a new communication standard. For example, the newcommunication standard may be an extreme high throughput (EHT) standardwhich is currently being discussed. The EHT standard may use anincreased bandwidth, an enhanced PHY layer protocol data unit (PPDU)structure, an enhanced sequence, a hybrid automatic repeat request(HARQ) scheme, or the like, which is newly proposed. The EHT standardmay be called the IEEE 802.11be standard.

SUMMARY

In the EHT standard, a wide bandwidth (e.g., 160/320 MHz), 16 streams,and/or a multi-link (or multi-band) operation may be used to supporthigh throughput and high data rate.

In the EHT standard, a device supporting a multi-link (i.e., amulti-link device) may operate in a plurality of links. The multi-linkdevice needs to transmit element information on a second link through afirst link. Accordingly, a technical feature for the multi-link deviceto receive information on a different link may be required.

According to various embodiments, a multi-link device (MLD) operating ina plurality of links may perform: an operation of receiving a physicallayer protocol data unit (PPDU) through a first link among the pluralityof links, the PPDU including a first information field related to asecond link distinct from the first link among the plurality of links,and the first information field related to the second link including asecond information field related to a link identifier of the second linkand a third information field related to whether complete elementinformation for the second link is included in the PPDU; and anoperation of obtaining the complete element information for the secondlink based on the second information field and the third informationfield.

A STA included in a multi-link device may also transmit information onanother STA (or link) in the multi-link device through one link.Accordingly, it is possible to reduce overhead of a frame exchange. Inaddition, it is possible to increase link use efficiency of the STA andto reduce power consumption.

In addition, the multi-link device may receive a PPDU including elementinformation on a second link through a first link. The PPDU may includean information field for indicating whether complete element informationfor the second link is included in the PPDU. Accordingly, the multi-linkdevice may determine whether the complete element information for thesecond link is included in the received PPDU, and may obtain/identifythe complete element information for the second link based thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a transmitting apparatus and/or receivingapparatus of the present specification.

FIG. 2 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

FIG. 3 illustrates a general link setup process.

FIG. 4 illustrates an example of a PPDU used in an IEEE standard.

FIG. 5 illustrates an operation based on UL-MU.

FIG. 6 illustrates an example of a trigger frame.

FIG. 7 illustrates an example of a common information field of a triggerframe.

FIG. 8 illustrates an example of a subfield included in a per userinformation field.

FIG. 9 illustrates an example of a channel used/supported/defined withina 2.4 GHz band.

FIG. 10 illustrates an example of a channel used/supported/definedwithin a 5 GHz band.

FIG. 11 illustrates an example of a channel used/supported/definedwithin a 6 GHz band.

FIG. 12 shows an example of a HE-PPDU.

FIG. 13 illustrates an example of a PPDU used in the presentspecification.

FIG. 14 illustrates an example of a modified transmission device and/orreceiving device of the present specification.

FIG. 15 illustrates an example of channel bonding.

FIG. 16 illustrates an example of the structure of a non-AP MLD.

FIG. 17 illustrates an example in which an AP MLD and a non-AP MLD areconnected through a link setup process.

FIG. 18 illustrates an example in which a link is changed orreconnected.

FIG. 19 illustrates a specific example in which a link is changed orreconnected.

FIG. 20 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 21 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 22 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 23 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 24 illustrates a specific example of a STA ratio per link.

FIG. 25 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 26 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 27 illustrates an example of an MLD structure supporting ananchored link.

FIG. 28 illustrates an example of a situation in which an anchored linkchange or reconnection is required.

FIG. 29 illustrates the operations of an AP MLD and a non-AP MLD for ananchored link change or reconnection.

FIG. 30 and FIG. 31 illustrate specific examples of an element for ananchored link reconnection.

FIG. 32 is a flowchart illustrating the operation of a multi-linkdevice.

FIG. 33 is a flowchart illustrating the operation of an AP multi-linkdevice.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the present specification, “A or B” may mean “only A”, “only B” or“both A and B”. In other words, in the present specification, “A or B”may be interpreted as “A and/or B”. For example, in the presentspecification, “A, B, or C” may mean “only A”, “only B”, “only C”, or“any combination of A, B, C”.

A slash (/) or comma used in the present specification may mean“and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B”may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C”may mean “A, B, or C”.

In the present specification, “at least one of A and B” may mean “onlyA”, “only B”, or “both A and B”. In addition, in the presentspecification, the expression “at least one of A or B” or “at least oneof A and/or B” may be interpreted as “at least one of A and B”.

In addition, in the present specification, “at least one of A, B, and C”may mean “only A”, “only B”, “only C”, or “any combination of A, B, andC”. In addition, “at least one of A, B, or C” or “at least one of A, B,and/or C” may mean “at least one of A, B, and C”.

In addition, a parenthesis used in the present specification may mean“for example”. Specifically, when indicated as “control information(EHT-signal)”, it may denote that “EHT-signal” is proposed as an exampleof the “control information”. In other words, the “control information”of the present specification is not limited to “EHT-signal”, and“EHT-signal” may be proposed as an example of the “control information”.In addition, when indicated as “control information (i.e., EHT-signal)”,it may also mean that “EHT-signal” is proposed as an example of the“control information”.

Technical features described individually in one figure in the presentspecification may be individually implemented, or may be simultaneouslyimplemented.

The following example of the present specification may be applied tovarious wireless communication systems. For example, the followingexample of the present specification may be applied to a wireless localarea network (WLAN) system. For example, the present specification maybe applied to the IEEE 802.11a/g/n/ac standard or the IEEE 802.11axstandard. In addition, the present specification may also be applied tothe newly proposed EHT standard or IEEE 802.11be standard. In addition,the example of the present specification may also be applied to a newWLAN standard enhanced from the EHT standard or the IEEE 802.11bestandard. In addition, the example of the present specification may beapplied to a mobile communication system. For example, it may be appliedto a mobile communication system based on long term evolution (LTE)depending on a 3^(rd) generation partnership project (3GPP) standard andbased on evolution of the LTE. In addition, the example of the presentspecification may be applied to a communication system of a 5G NRstandard based on the 3GPP standard.

Hereinafter, in order to describe a technical feature of the presentspecification, a technical feature applicable to the presentspecification will be described.

FIG. 1 shows an example of a transmitting apparatus and/or receivingapparatus of the present specification.

In the example of FIG. 1 , various technical features described belowmay be performed. FIG. 1 relates to at least one station (STA). Forexample, STAs 110 and 120 of the present specification may also becalled in various terms such as a mobile terminal, a wireless device, awireless transmit/receive unit (WTRU), a user equipment (UE), a mobilestation (MS), a mobile subscriber unit, or simply a user. The STAs 110and 120 of the present specification may also be called in various termssuch as a network, a base station, a node-B, an access point (AP), arepeater, a router, a relay, or the like. The STAs 110 and 120 of thepresent specification may also be referred to as various names such as areceiving apparatus, a transmitting apparatus, a receiving STA, atransmitting STA, a receiving device, a transmitting device, or thelike.

For example, the STAs 110 and 120 may serve as an AP or a non-AP. Thatis, the STAs 110 and 120 of the present specification may serve as theAP and/or the non-AP.

The STAs 110 and 120 of the present specification may support variouscommunication standards together in addition to the IEEE 802.11standard. For example, a communication standard (e.g., LTE, LTE-A, 5G NRstandard) or the like based on the 3GPP standard may be supported. Inaddition, the STA of the present specification may be implemented asvarious devices such as a mobile phone, a vehicle, a personal computer,or the like. In addition, the STA of the present specification maysupport communication for various communication services such as voicecalls, video calls, data communication, and self-driving(autonomous-driving), or the like.

The STAs 110 and 120 of the present specification may include a mediumaccess control (MAC) conforming to the IEEE 802.11 standard and aphysical layer interface for a radio medium.

The STAs 110 and 120 will be described below with reference to asub-figure (a) of FIG. 1 .

The first STA 110 may include a processor 111, a memory 112, and atransceiver 113. The illustrated process, memory, and transceiver may beimplemented individually as separate chips, or at least twoblocks/functions may be implemented through a single chip.

The transceiver 113 of the first STA performs a signaltransmission/reception operation. Specifically, an IEEE 802.11 packet(e.g., IEEE 802.11a/b/g/n/ac/ax/be, etc.) may be transmitted/received.

For example, the first STA 110 may perform an operation intended by anAP. For example, the processor 111 of the AP may receive a signalthrough the transceiver 113, process a reception (RX) signal, generate atransmission (TX) signal, and provide control for signal transmission.The memory 112 of the AP may store a signal (e.g., RX signal) receivedthrough the transceiver 113, and may store a signal (e.g., TX signal) tobe transmitted through the transceiver.

For example, the second STA 120 may perform an operation intended by anon-AP STA. For example, a transceiver 123 of a non-AP performs a signaltransmission/reception operation. Specifically, an IEEE 802.11 packet(e.g., IEEE 802.11a/b/g/n/ac/ax/be packet, etc.) may betransmitted/received.

For example, a processor 121 of the non-AP STA may receive a signalthrough the transceiver 123, process an RX signal, generate a TX signal,and provide control for signal transmission. A memory 122 of the non-APSTA may store a signal (e.g., RX signal) received through thetransceiver 123, and may store a signal (e.g., TX signal) to betransmitted through the transceiver.

For example, an operation of a device indicated as an AP in thespecification described below may be performed in the first STA 110 orthe second STA 120. For example, if the first STA 110 is the AP, theoperation of the device indicated as the AP may be controlled by theprocessor 111 of the first STA 110, and a related signal may betransmitted or received through the transceiver 113 controlled by theprocessor 111 of the first STA 110. In addition, control informationrelated to the operation of the AP or a TX/RX signal of the AP may bestored in the memory 112 of the first STA 110. In addition, if thesecond STA 120 is the AP, the operation of the device indicated as theAP may be controlled by the processor 121 of the second STA 120, and arelated signal may be transmitted or received through the transceiver123 controlled by the processor 121 of the second STA 120. In addition,control information related to the operation of the AP or a TX/RX signalof the AP may be stored in the memory 122 of the second STA 120.

For example, in the specification described below, an operation of adevice indicated as a non-AP (or user-STA) may be performed in the firstSTA 110 or the second STA 120. For example, if the second STA 120 is thenon-AP, the operation of the device indicated as the non-AP may becontrolled by the processor 121 of the second STA 120, and a relatedsignal may be transmitted or received through the transceiver 123controlled by the processor 121 of the second STA 120. In addition,control information related to the operation of the non-AP or a TX/RXsignal of the non-AP may be stored in the memory 122 of the second STA120. For example, if the first STA 110 is the non-AP, the operation ofthe device indicated as the non-AP may be controlled by the processor111 of the first STA 110, and a related signal may be transmitted orreceived through the transceiver 113 controlled by the processor 111 ofthe first STA 110. In addition, control information related to theoperation of the non-AP or a TX/RX signal of the non-AP may be stored inthe memory 112 of the first STA 110.

In the specification described below, a device called a(transmitting/receiving) STA, a first STA, a second STA, a STA1, a STA2,an AP, a first AP, a second AP, an AN, an AP2, a(transmitting/receiving) terminal, a (transmitting/receiving) device, a(transmitting/receiving) apparatus, a network, or the like may imply theSTAs 110 and 120 of FIG. 1 . For example, a device indicated as, withouta specific reference numeral, the (transmitting/receiving) STA, thefirst STA, the second STA, the STA1, the STA2, the AP, the first AP, thesecond AP, the AN, the AP2, the (transmitting/receiving) terminal, the(transmitting/receiving) device, the (transmitting/receiving) apparatus,the network, or the like may imply the STAs 110 and 120 of FIG. 1 . Forexample, in the following example, an operation in which various STAstransmit/receive a signal (e.g., a PPDU) may be performed in thetransceivers 113 and 123 of FIG. 1 . In addition, in the followingexample, an operation in which various STAs generate a TX/RX signal orperform data processing and computation in advance for the TX/RX signalmay be performed in the processors 111 and 121 of FIG. 1 . For example,an example of an operation for generating the TX/RX signal or performingthe data processing and computation in advance may include: 1) anoperation ofdetermining/obtaining/configuring/computing/decoding/encoding bitinformation of a sub-field (SIG, STF, LTF, Data) included in a PPDU; 2)an operation of determining/configuring/obtaining a time resource orfrequency resource (e.g., a subcarrier resource) or the like used forthe sub-field (SIG, STF, LTF, Data) included the PPDU; 3) an operationof determining/configuring/obtaining a specific sequence (e.g., a pilotsequence, an STF/LTF sequence, an extra sequence applied to SIG) or thelike used for the sub-field (SIG, STF, LTF, Data) field included in thePPDU; 4) a power control operation and/or power saving operation appliedfor the STA; and 5) an operation related todetermining/obtaining/configuring/decoding/encoding or the like of anACK signal. In addition, in the following example, a variety ofinformation used by various STAs fordetermining/obtaining/configuring/computing/decoding/decoding a TX/RXsignal (e.g., information related to a field/subfield/controlfield/parameter/power or the like) may be stored in the memories 112 and122 of FIG. 1 .

The aforementioned device/STA of the sub-figure (a) of FIG. 1 may bemodified as shown in the sub-figure (b) of FIG. 1 . Hereinafter, theSTAs 110 and 120 of the present specification will be described based onthe sub-figure (b) of FIG. 1 .

For example, the transceivers 113 and 123 illustrated in the sub-figure(b) of FIG. 1 may perform the same function as the aforementionedtransceiver illustrated in the sub-figure (a) of FIG. 1 . For example,processing chips 114 and 124 illustrated in the sub-figure (b) of FIG. 1may include the processors 111 and 121 and the memories 112 and 122. Theprocessors 111 and 121 and memories 112 and 122 illustrated in thesub-figure (b) of FIG. 1 may perform the same function as theaforementioned processors 111 and 121 and memories 112 and 122illustrated in the sub-figure (a) of FIG. 1 .

A mobile terminal, a wireless device, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobilesubscriber unit, a user, a user STA, a network, a base station, aNode-B, an access point (AP), a repeater, a router, a relay, a receivingunit, a transmitting unit, a receiving STA, a transmitting STA, areceiving device, a transmitting device, a receiving apparatus, and/or atransmitting apparatus, which are described below, may imply the STAs110 and 120 illustrated in the sub-figure (a)/(b) of FIG. 1 , or mayimply the processing chips 114 and 124 illustrated in the sub-figure (b)of FIG. 1 . That is, a technical feature of the present specificationmay be performed in the STAs 110 and 120 illustrated in the sub-figure(a)/(b) of FIG. 1 , or may be performed only in the processing chips 114and 124 illustrated in the sub-figure (b) of FIG. 1 . For example, atechnical feature in which the transmitting STA transmits a controlsignal may be understood as a technical feature in which a controlsignal generated in the processors 111 and 121 illustrated in thesub-figure (a)/(b) of FIG. 1 is transmitted through the transceivers 113and 123 illustrated in the sub-figure (a)/(b) of FIG. 1 . Alternatively,the technical feature in which the transmitting STA transmits thecontrol signal may be understood as a technical feature in which thecontrol signal to be transferred to the transceivers 113 and 123 isgenerated in the processing chips 114 and 124 illustrated in thesub-figure (b) of FIG. 1 .

For example, a technical feature in which the receiving STA receives thecontrol signal may be understood as a technical feature in which thecontrol signal is received by means of the transceivers 113 and 123illustrated in the sub-figure (a) of FIG. 1 . Alternatively, thetechnical feature in which the receiving STA receives the control signalmay be understood as the technical feature in which the control signalreceived in the transceivers 113 and 123 illustrated in the sub-figure(a) of FIG. 1 is obtained by the processors 111 and 121 illustrated inthe sub-figure (a) of FIG. 1 . Alternatively, the technical feature inwhich the receiving STA receives the control signal may be understood asthe technical feature in which the control signal received in thetransceivers 113 and 123 illustrated in the sub-figure (b) of FIG. 1 isobtained by the processing chips 114 and 124 illustrated in thesub-figure (b) of FIG. 1 .

Referring to the sub-figure (b) of FIG. 1 , software codes 115 and 125may be included in the memories 112 and 122. The software codes 115 and126 may include instructions for controlling an operation of theprocessors 111 and 121. The software codes 115 and 125 may be includedas various programming languages.

The processors 111 and 121 or processing chips 114 and 124 of FIG. 1 mayinclude an application-specific integrated circuit (ASIC), otherchipsets, a logic circuit and/or a data processing device. The processormay be an application processor (AP). For example, the processors 111and 121 or processing chips 114 and 124 of FIG. 1 may include at leastone of a digital signal processor (DSP), a central processing unit(CPU), a graphics processing unit (GPU), and a modulator and demodulator(modem). For example, the processors 111 and 121 or processing chips 114and 124 of FIG. 1 may be SNAPDRAGON™ series of processors made byQualcomm®, EXYNOS™ series of processors made by Samsung®, A series ofprocessors made by Apple®, HELIO™ series of processors made byMediaTek®, ATOM™ series of processors made by Intel® or processorsenhanced from these processors.

In the present specification, an uplink may imply a link forcommunication from a non-AP STA to an SP STA, and an uplinkPPDU/packet/signal or the like may be transmitted through the uplink. Inaddition, in the present specification, a downlink may imply a link forcommunication from the AP STA to the non-AP STA, and a downlinkPPDU/packet/signal or the like may be transmitted through the downlink.

FIG. 2 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

An upper part of FIG. 2 illustrates the structure of an infrastructurebasic service set (BSS) of institute of electrical and electronicengineers (i.e. EE) 802.11.

Referring the upper part of FIG. 2 , the wireless LAN system may includeone or more infrastructure BSSs 200 and 205 (hereinafter, referred to asBSS). The BSSs 200 and 205 as a set of an AP and a STA such as an accesspoint (AP) 225 and a station (STA1) 200-1 which are successfullysynchronized to communicate with each other are not concepts indicatinga specific region. The BSS 205 may include one or more STAs 205-1 and205-2 which may be joined to one AP 230.

The BSS may include at least one STA, APs providing a distributionservice, and a distribution system (DS) 210 connecting multiple APs.

The distribution system 210 may implement an extended service set (ESS)240 extended by connecting the multiple BSSs 200 and 205. The ESS 240may be used as a term indicating one network configured by connectingone or more APs 225 or 230 through the distribution system 210. The APincluded in one ESS 240 may have the same service set identification(SSID).

A portal 220 may serve as a bridge which connects the wireless LANnetwork (i.e. EE 802.11) and another network (e.g., 802.X).

In the BSS illustrated in the upper part of FIG. 2 , a network betweenthe APs 225 and 230 and a network between the APs 225 and 230 and theSTAs 200-1, 205-1, and 205-2 may be implemented. However, the network isconfigured even between the STAs without the APs 225 and 230 to performcommunication. A network in which the communication is performed byconfiguring the network even between the STAs without the APs 225 and230 is defined as an Ad-Hoc network or an independent basic service set(IBSS).

A lower part of FIG. 2 illustrates a conceptual view illustrating theIBSS.

Referring to the lower part of FIG. 2 , the IBSS is a BSS that operatesin an Ad-Hoc mode. Since the IBSS does not include the access point(AP), a centralized management entity that performs a managementfunction at the center does not exist. That is, in the IBSS, STAs 250-1,250-2, 250-3, 255-4, and 255-5 are managed by a distributed manner. Inthe IBSS, all STAs 250-1, 250-2, 250-3, 255-4, and 255-5 may beconstituted by movable STAs and are not permitted to access the DS toconstitute a self-contained network.

FIG. 3 illustrates a general link setup process.

In S310, a STA may perform a network discovery operation. The networkdiscovery operation may include a scanning operation of the STA. Thatis, to access a network, the STA needs to discover a participatingnetwork. The STA needs to identify a compatible network beforeparticipating in a wireless network, and a process of identifying anetwork present in a particular area is referred to as scanning Scanningmethods include active scanning and passive scanning.

FIG. 3 illustrates a network discovery operation including an activescanning process. In active scanning, a STA performing scanningtransmits a probe request frame and waits for a response to the proberequest frame in order to identify which AP is present around whilemoving to channels. A responder transmits a probe response frame as aresponse to the probe request frame to the STA having transmitted theprobe request frame. Here, the responder may be a STA that transmits thelast beacon frame in a BSS of a channel being scanned. In the BSS, sincean AP transmits a beacon frame, the AP is the responder. In an IBSS,since STAs in the IBSS transmit a beacon frame in turns, the responderis not fixed. For example, when the STA transmits a probe request framevia channel 1 and receives a probe response frame via channel 1, the STAmay store BSS-related information included in the received proberesponse frame, may move to the next channel (e.g., channel 2), and mayperform scanning (e.g., transmits a probe request and receives a proberesponse via channel 2) by the same method.

Although not shown in FIG. 3 , scanning may be performed by a passivescanning method. In passive scanning, a STA performing scanning may waitfor a beacon frame while moving to channels. A beacon frame is one ofmanagement frames in IEEE 802.11 and is periodically transmitted toindicate the presence of a wireless network and to enable the STAperforming scanning to find the wireless network and to participate inthe wireless network. In a BSS, an AP serves to periodically transmit abeacon frame. In an IBSS, STAs in the IBSS transmit a beacon frame inturns. Upon receiving the beacon frame, the STA performing scanningstores information related to a BSS included in the beacon frame andrecords beacon frame information in each channel while moving to anotherchannel. The STA having received the beacon frame may store BSS-relatedinformation included in the received beacon frame, may move to the nextchannel, and may perform scanning in the next channel by the samemethod.

After discovering the network, the STA may perform an authenticationprocess in S320. The authentication process may be referred to as afirst authentication process to be clearly distinct from the followingsecurity setup operation in S340. The authentication process in S320 mayinclude a process in which the STA transmits an authentication requestframe to the AP and the AP transmits an authentication response frame tothe STA in response. The authentication frames used for anauthentication request/response are management frames.

The authentication frames may include information related to anauthentication algorithm number, an authentication transaction sequencenumber, a status code, a challenge text, a robust security network(RSN), and a finite cyclic group.

The STA may transmit the authentication request frame to the AP. The APmay determine whether to allow the authentication of the STA based onthe information included in the received authentication request frame.The AP may provide the authentication processing result to the STA viathe authentication response frame.

When the STA is successfully authenticated, the STA may perform anassociation process in S330. The association process includes a processin which the STA transmits an association request frame to the AP andthe AP transmits an association response frame to the STA in response.The association request frame may include, for example, informationrelated to various capabilities, a beacon listen interval, a service setidentifier (SSID), a supported rate, a supported channel, RSN, amobility domain, a supported operating class, a traffic indication map(TIM) broadcast request, and an interworking service capability. Theassociation response frame may include, for example, information relatedto various capabilities, a status code, an association ID (AID), asupported rate, an enhanced distributed channel access (EDCA) parameterset, a received channel power indicator (RCPI), a receivedsignal-to-noise indicator (RSNI), a mobility domain, a timeout interval(association comeback time), an overlapping BSS scanning parameter, aTIM broadcast response, and a QoS map.

In S340, the STA may perform a security setup process. The securitysetup process in S340 may include a process of setting up a private keythrough four-way handshaking, for example, through an extensibleauthentication protocol over LAN (EAPOL) frame.

FIG. 4 illustrates an example of a PPDU used in an IEEE standard.

As illustrated, various types of PHY protocol data units (PPDUs) areused in IEEE a/g/n/ac standards. Specifically, an LTF and a STF includea training signal, a SIG-A and a SIG-B include control information for areceiving STA, and a data field includes user data corresponding to aPSDU (MAC PDU/aggregated MAC PDU).

FIG. 4 also includes an example of an HE PPDU according to IEEE802.11ax. The HE PPDU according to FIG. 4 is an illustrative PPDU formultiple users. An HE-SIG-B may be included only in a PPDU for multipleusers, and an HE-SIG-B may be omitted in a PPDU for a single user.

As illustrated in FIG. 4 , the HE-PPDU for multiple users (MUs) mayinclude a legacy-short training field (L-STF), a legacy-long trainingfield (L-LTF), a legacy-signal (L-SIG), a high efficiency-signal A(HE-SIG A), a high efficiency-signal-B (HE-SIG B), a highefficiency-short training field (HE-STF), a high efficiency-longtraining field (HE-LTF), a data field (alternatively, an MAC payload),and a packet extension (PE) field. The respective fields may betransmitted for illustrated time periods (i.e., 4 or 8 μs).

Hereinafter, a resource unit (RU) used for a PPDU is described. An RUmay include a plurality of subcarriers (or tones). An RU may be used totransmit a signal to a plurality of STAs according to OFDMA. Further, anRU may also be defined to transmit a signal to one STA. An RU may beused for an STF, an LTF, a data field, or the like.

FIG. 5 illustrates an operation based on UL-MU. As illustrated, atransmitting STA (e.g., an AP) may perform channel access throughcontending (e.g., a backoff operation), and may transmit a trigger frame530. That is, the transmitting STA may transmit a PPDU including thetrigger frame 530. Upon receiving the PPDU including the trigger frame,a trigger-based (TB) PPDU is transmitted after a delay corresponding toSIFS.

TB PPDUs 541 and 542 may be transmitted at the same time period, and maybe transmitted from a plurality of STAs (e.g., user STAs) having AIDsindicated in the trigger frame 530. An ACK frame 550 for the TB PPDU maybe implemented in various forms.

A specific feature of the trigger frame is described with reference toFIG. 6 to FIG. 8 . Even if UL-MU communication is used, an orthogonalfrequency division multiple access (OFDMA) scheme or a MU MIMO schememay be used, and the OFDMA and MU-MIMO schemes may be simultaneouslyused.

FIG. 6 illustrates an example of a trigger frame. The trigger frame ofFIG. 6 allocates a resource for uplink multiple-user (MU) transmission,and may be transmitted, for example, from an AP. The trigger frame maybe configured of a MAC frame, and may be included in a PPDU.

Each field shown in FIG. 6 may be partially omitted, and another fieldmay be added. In addition, a length of each field may be changed to bedifferent from that shown in the figure.

A frame control field 610 of FIG. 6 may include information related to aMAC protocol version and extra additional control information. Aduration field 620 may include time information for NAV configuration orinformation related to an identifier (e.g., AID) of a STA.

In addition, an RA field 630 may include address information of areceiving STA of a corresponding trigger frame, and may be optionallyomitted. A TA field 640 may include address information of a STA (e.g.,an AP) which transmits the corresponding trigger frame. A commoninformation field 650 includes common control information applied to thereceiving STA which receives the corresponding trigger frame. Forexample, a field indicating a length of an L-SIG field of an uplink PPDUtransmitted in response to the corresponding trigger frame orinformation for controlling content of a SIG-A field (i.e., HE-SIG-Afield) of the uplink PPDU transmitted in response to the correspondingtrigger frame may be included. In addition, as common controlinformation, information related to a length of a CP of the uplink PPDUtransmitted in response to the corresponding trigger frame orinformation related to a length of an LTF field may be included.

In addition, per user information fields 660 #1 to 660 #N correspondingto the number of receiving STAs which receive the trigger frame of FIG.6 are preferably included. The per user information field may also becalled an “allocation field”.

In addition, the trigger frame of FIG. 6 may include a padding field 670and a frame check sequence field 680.

Each of the per user information fields 660 #1 to 660 #N shown in FIG. 6may include a plurality of subfields.

FIG. 7 illustrates an example of a common information field of a triggerframe. A subfield of FIG. 7 may be partially omitted, and an extrasubfield may be added. In addition, a length of each subfieldillustrated may be changed.

A length field 710 illustrated has the same value as a length field ofan L-SIG field of an uplink PPDU transmitted in response to acorresponding trigger frame, and a length field of the L-SIG field ofthe uplink PPDU indicates a length of the uplink PPDU. As a result, thelength field 710 of the trigger frame may be used to indicate the lengthof the corresponding uplink PPDU.

In addition, a cascade identifier field 720 indicates whether a cascadeoperation is performed. The cascade operation implies that downlink MUtransmission and uplink MU transmission are performed together in thesame TXOP. That is, it implies that downlink MU transmission isperformed and thereafter uplink MU transmission is performed after apre-set time (e.g., SIFS). During the cascade operation, only onetransmitting device (e.g., AP) may perform downlink communication, and aplurality of transmitting devices (e.g., non-APs) may perform uplinkcommunication.

A CS request field 730 indicates whether a wireless medium state or aNAV or the like is necessarily considered in a situation where areceiving device which has received a corresponding trigger frametransmits a corresponding uplink PPDU.

An HE-SIG-A information field 740 may include information forcontrolling content of a SIG-A field (i.e., HE-SIG-A field) of theuplink PPDU in response to the corresponding trigger frame.

A CP and LTF type field 750 may include information related to a CPlength and LTF length of the uplink PPDU transmitted in response to thecorresponding trigger frame. A trigger type field 760 may indicate apurpose of using the corresponding trigger frame, for example, typicaltriggering, triggering for beamforming, a request for block ACK/NACK, orthe like.

It may be assumed that the trigger type field 760 of the trigger framein the present specification indicates a trigger frame of a basic typefor typical triggering. For example, the trigger frame of the basic typemay be referred to as a basic trigger frame.

FIG. 8 illustrates an example of a subfield included in a per userinformation field. A user information field 800 of FIG. 8 may beunderstood as any one of the per user information fields 1160 #1 to 1160#N mentioned above with reference to FIG. 11 . A subfield included inthe user information field 80 of FIG. 8 may be partially omitted, and anextra subfield may be added. In addition, a length of each subfieldillustrated may be changed.

A user identifier field 810 of FIG. 8 indicates an identifier of a STA(i.e., receiving STA) corresponding to per user information. An exampleof the identifier may be the entirety or part of an associationidentifier (AID) value of the receiving STA.

In addition, an RU allocation field 820 may be included. That is, whenthe receiving STA identified through the user identifier field 810transmits a TB PPDU in response to the trigger frame, the TB PPDU istransmitted through an RU indicated by the RU allocation field 820.

The subfield of FIG. 8 may include a coding type field 830. The codingtype field 830 may indicate a coding type of the TB PPDU. For example,when BCC coding is applied to the TB PPDU, the coding type field 830 maybe set to ‘1’, and when LDPC coding is applied, the coding type field830 may be set to ‘0’.

In addition, the subfield of FIG. 8 may include an MCS field 840. TheMCS field 840 may indicate an MCS scheme applied to the TB PPDU. Forexample, when BCC coding is applied to the TB PPDU, the coding typefield 830 may be set to ‘1’, and when LDPC coding is applied, the codingtype field 830 may be set to ‘0’.

FIG. 9 illustrates an example of a channel used/supported/defined withina 2.4 GHz band.

The 2.4 GHz band may be called in other terms such as a first band. Inaddition, the 2.4 GHz band may imply a frequency domain in whichchannels of which a center frequency is close to 2.4 GHz (e.g., channelsof which a center frequency is located within 2.4 to 2.5 GHz) areused/supported/defined.

A plurality of 20 MHz channels may be included in the 2.4 GHz band. 20MHz within the 2.4 GHz may have a plurality of channel indices (e.g., anindex 1 to an index 14). For example, a center frequency of a 20 MHzchannel to which a channel index 1 is allocated may be 2.412 GHz, acenter frequency of a 20 MHz channel to which a channel index 2 isallocated may be 2.417 GHz, and a center frequency of a 20 MHz channelto which a channel index N is allocated may be (2.407+0.005*N) GHz. Thechannel index may be called in various terms such as a channel number orthe like. Specific numerical values of the channel index and centerfrequency may be changed.

FIG. 9 exemplifies 4 channels within a 2.4 GHz band. Each of 1st to 4thfrequency domains 910 to 940 shown herein may include one channel. Forexample, the 1st frequency domain 910 may include a channel 1 (a 20 MHzchannel having an index 1). In this case, a center frequency of thechannel 1 may be set to 2412 MHz. The 2nd frequency domain 920 mayinclude a channel 6. In this case, a center frequency of the channel 6may be set to 2437 MHz. The 3rd frequency domain 930 may include achannel 11. In this case, a center frequency of the channel 11 may beset to 2462 MHz. The 4th frequency domain 940 may include a channel 14.In this case, a center frequency of the channel 14 may be set to 2484MHz.

FIG. 10 illustrates an example of a channel used/supported/definedwithin a 5 GHz band.

The 5 GHz band may be called in other terms such as a second band or thelike. The 5 GHz band may imply a frequency domain in which channels ofwhich a center frequency is greater than or equal to 5 GHz and less than6 GHz (or less than 5.9 GHz) are used/supported/defined. Alternatively,the 5 GHz band may include a plurality of channels between 4.5 GHz and5.5 GHz. A specific numerical value shown in FIG. 10 may be changed.

A plurality of channels within the 5 GHz band include an unlicensednational information infrastructure (UNII)-1, a UNII-2, a UNII-3, and anISM. The INII-1 may be called UNII Low. The UNII-2 may include afrequency domain called UNII Mid and UNII-2Extended. The UNII-3 may becalled UNII-Upper.

A plurality of channels may be configured within the 5 GHz band, and abandwidth of each channel may be variously set to, for example, 20 MHz,40 MHz, 80 MHz, 160 MHz, or the like. For example, 5170 MHz to 5330 MHzfrequency domains/ranges within the UNII-1 and UNII-2 may be dividedinto eight 20 MHz channels. The 5170 MHz to 5330 MHz frequencydomains/ranges may be divided into four channels through a 40 MHzfrequency domain. The 5170 MHz to 5330 MHz frequency domains/ranges maybe divided into two channels through an 80 MHz frequency domain.Alternatively, the 5170 MHz to 5330 MHz frequency domains/ranges may bedivided into one channel through a 160 MHz frequency domain.

FIG. 11 illustrates an example of a channel used/supported/definedwithin a 6 GHz band.

The 6 GHz band may be called in other terms such as a third band or thelike. The 6 GHz band may imply a frequency domain in which channels ofwhich a center frequency is greater than or equal to 5.9 GHz areused/supported/defined. A specific numerical value shown in FIG. 11 maybe changed.

For example, the 20 MHz channel of FIG. 11 may be defined starting from5.940 GHz. Specifically, among 20 MHz channels of FIG. 11 , the leftmostchannel may have an index 1 (or a channel index, a channel number,etc.), and 5.945 GHz may be assigned as a center frequency. That is, acenter frequency of a channel of an index N may be determined as(5.940+0.005*N) GHz.

Accordingly, an index (or channel number) of the 2 MHz channel of FIG.11 may be 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61,65, 69, 73, 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125,129, 133, 137, 141, 145, 149, 153, 157, 161, 165, 169, 173, 177, 181,185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 233. Inaddition, according to the aforementioned (5.940+0.005*N) GHz rule, anindex of the 40 MHz channel of FIG. 17 may be 3, 11, 19, 27, 35, 43, 51,59, 67, 75, 83, 91, 99, 107, 115, 123, 131, 139, 147, 155, 163, 171,179, 187, 195, 203, 211, 219, 227.

Although 20, 40, 80, and 160 MHz channels are illustrated in the exampleof FIG. 11 , a 240 MHz channel or a 320 MHz channel may be additionallyadded.

Hereinafter, a PPDU transmitted/received in a STA of the presentspecification will be described.

FIG. 12 shows an example of a HE-PPDU.

The illustrated L-STF 1200 may include a short training orthogonalfrequency division multiplexing symbol (OFDM). The L-STF 1200 may beused for frame detection, automatic gain control (AGC), diversitydetection, and coarse frequency/time synchronization.

The L-LTF 1210 may include a long training orthogonal frequency divisionmultiplexing symbol (OFDM). The L-LTF 1210 may be used for finefrequency/time synchronization and channel estimation.

The L-SIG 1220 may be used to transmit control information. The L-SIG1220 may include information related to a data transmission rate and adata length. Also, the L-SIG 1220 may be repeatedly transmitted. Thatis, the L-SIG 1220 may be configured in a repeated format (e.g., may bereferred to as R-LSIG).

The HE-SIG-A 1230 may include control information common to thereceiving station(s).

Specifically, the HE-SIG-A 1230 may include information related to: 1) aDL/UL indicator; 2) a BSS color field that is an identifier of the BSS;3) a field indicating the remaining time of the current TXOPduration/period; 4) a Bandwidth field indicating whether 20, 40, 80,160, 80+80 MHz; 5) a field indicating MCS scheme applied to theHE-SIG-B; 6) an indication field indicating whether modulation dualsubcarrier modulation (DCM) is applied to the HE-SIG-B for MCS; 7) afield indicating the number of symbols used for HE-SIG-B; 8) a fieldindicating whether the HE-SIG-B is generated over the full/entire band;9) a field indicating the number of symbols of the HE-LTF; 10) a fieldindicating a length of the HE-LTF and a CP length; 11) a fieldindicating whether additional OFDM symbols exist for LDPC coding; 12) afield indicating control information on Packet Extension (PE); and/or13) a field indicating information related to a CRC field of theHE-SIG-A, and the like. At least one field of the HE-SIG-A may beomitted or changed. In addition, some fields may be added or omitted inother environments where the HE-SIG-A is not a multi-user (MU)environment.

Also, the HE-SIG-A 1230 may be composed of two parts: HE-SIG-A1 andHE-SIG-A2. The HE-SIG-A1 and HE-SIG-A2 included in the HE-SIG-A may bedefined in the following format structure (field) according to acorresponding PPDU. First, the HE-SIG-A field of the HE SU PPDU may bedefined as follows.

TABLE 1 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU froman HE TB PPDU: Set to 1 for an HE SU PPDU and HE ER SU PPDU B1 Beam 1Set to 1 to indicate that the pre-HE modulated fields of Change the PPDUare spatially mapped differently from the first symbol of the HE-LTF.Equation (28-6), Equation (28-9), Equation (28-12), Equation (28-14),Equation (28-16) and Equation (28-18) apply if the Beam Change field isset to 1. Set to 0 to indicate that the pre-HE modulated fields of thePPDU are spatially mapped the same way as the first symbol of the HE-LTFon each tone. Equation (28- 8), Equation (28-10), Equation (28-13),Equation (28- 15), Equation (28-17) and Equation (28-19) apply if theBeam Change field is set to 0. B2 UL/DL 1 Indicates whether the PPDU issent UL or DL. Set to the value indicated by the TXVECTOR parameterUPLINK_FLAG. B3-B6 MCS 4 For an HE SU PPDU: Set to n for MCSn, where n =0, 1, 2, . . . , 11 Values 12-15 are reserved For HE ER SU PPDU withBandwidth field set to 0 (242-tone RU): Set to n for MCSn, where n = 0,1, 2 Values 3-15 are reserved For HE ER SU PPDU with Bandwidth field setto 1 (upper frequency 106-tone RU): Set to 0 for MCS 0 Values 1-15 arereserved

TABLE 2 Number Bit Field of bits Description Two Parts of B7 DCM 1Indicates whether or not DCM is applied to the Data HE-SIG-A field forthe MCS indicated. If the STBC field is 0, then set to 1 to indicatethat DCM is applied to the Data field. Neither DCM nor STBC shall beapplied if both the DCM and STBC are set to 1. Set to 0 to indicate thatDCM is not applied to the Data field. NOTE-DCM is applied only toHE-MCSs 0, 1, 3 and 4. DCM is applied only to 1 and 2 spatial streams.DCM is not applied in combination with STBC B8-B13 BSS Color 6 The BSSColor field is an identifier of the BSS. Set to the value of theTXVECTOR parameter BSS_-COLOR. B14 Reserved 1 Reserved and set to 1B15-B18 Spatial Reuse 4 Indicates whether or not spatial reuse isallowed during the transmission of this PPDU Set to a value from Table28-21 (Spatial Reuse field encoding for an HE SU PPDU, HE ER SU PPDU,and HE MU PPDU), see 27.11.6 (SPATIAL_REUSE). Set to SRP_DISALLOW toprohibit SRP-based spatial reuse during this PPDU. Set toSRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP-based spatialreuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For theinterpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9(Spatial reuse operation). B19-B20 Bandwidth 2 For an HE SU PPDU: Set to0 for 20 MHz Set to 1 for 40 MHz Set to 2 for 80 MHz Set to 3 for 160MHz and 80 + 80 MHz For an HE ER SU PPDU: Set to 0 for 242-tone RU Setto 1 for upper frequency 106-tone RU within the primary 20 MHz Values 2and 3 are reserved

TABLE 3 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB21-B22 GI + LTF Size 2 Indicates the GI duration and HE-LTF size. Setto 0 to indicate a 1x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2xHE-LTF and 0.8 μs GI Set to 2 to indicate a 2x HE-LTF and 1.6 μs GI Setto 3 to indicate: a 4x HE-LTF and 0.8 μs GI if both the DCM and STBCfields are 1. Neither DCM nor STBC shall be applied if both the DCM andSTBC fields are set to 1. a 4x HE-LTF and 3.2 μs GI, otherwise B23-B25NSTS And 3 If the Doppler field is 0, indicates the number of space-Midamble time streams. Periodicity Set to the number of space-timestreams minus 1 For an HE ER SU PPDU, values 2 to 7 are reserved If theDoppler field is 1, then B23-B24 indicates the number of space timestreams, up to 4, and B25 indicates the midamble periodicity. B23-B24 isset to the number of space time streams minus 1. For an HE ER SU PPDU,values 2 and 3 are reserved B25 is set to 0 if TXVECTOR parameterMIDAMBLE_PERIODICITY is 10 and set to 1 if TXVECTOR parameterMIDAMBLE_PERIODICITY is 20. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 toindicate no duration information (HE SU PPDU) if TXVECTOR parameter orHE-SIG-A3 TXOP_DURATION is set to UNSPECIFIED. (HE ER SU PPDU) Set to avalue less than 127 to indicate duration information for NAV setting andprotection of the TXOP as follows: If TXVECTOR parameter TXOP_DURAT1ONis less than 512, then B0 is set to 0 and B1-B6 is set tofloor(TXOP_DURATION/8) Otherwise, B0 is set to 1 and B1-B6 is set tofloor ((TXOP_DURATION − 512)/128) where B0 indicates the TXOP lengthgranularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6indicates the scaled value of the TXOP_DURATION B7 Coding 1 Indicateswhether BCC or LDPC is used: Set to 0 to indicate BCC Set to 1 toindicate LDPC

TABLE 4 Number Bit Field of bits Description Two Parts of B8 LDPC Extra1 Indicates the presence of the extra OFDM symbol HE-SIG-A Symbolsegment for LDPC: Segment Set to 1 if an extra OFDM symbol segment forLDPC is present Set to 0 if an extra OFDM symbol segment for LDPC is notpresent Reserved and set to 1 if the Coding field is set to 0 B9 STBC 1If the DCM field is set to 0, then set to 1 if space time block codingis used. Neither DCM nor STBC shall be applied if both the DCM field andSTBC field are set to 1. Set to 0 otherwise. B10 Beam- 1 Set to 1 if abeamforming steering matrix is applied to formed the waveform in an SUtransmission. Set to 0 otherwise. B11-B12 Pre-FEC 2 Indicates thepre-FEC padding factor. Padding Set to 0 to indicate a pre-FEC paddingfactor of 4 Factor Set to 1 to indicate a pre-FEC padding factor of 1Set to 2 to indicate a pre-FEC padding factor of 2 Set to 3 to indicatea pre-FEC padding factor of 3 B13 PE Disambiguity 1 Indicates PEdisambiguity as defined in 28.3.12 (Packet extension). B14 Reserved 1Reserved and set to 1 B15 Doppler 1 Set to 1 if one of the followingapplies: The number of OFDM symbols in the Data field is larger than thesignaled midamble periodicity plus 1 and the midamble is present Thenumber of OFDM symbols in the Data field is less than or equal to thesignaled midamble periodicity plus 1 (see 28.3.11.16 Midamble), themidamble is not present, but the channel is fast varying. It recommendsthat midamble may be used for the PPDUs of the reverse link. Set to 0otherwise. B16-B19 CRC 4 CRC for bits 0-41 of the HE-SIG-A field (see28.3.10.7.3 (CRC computation)). Bits 0-41 of the HE-SIG-A fieldcorrespond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 ofHE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

In addition, the HE-SIG-A field of the HE MU PPDU may be defined asfollows.

TABLE 5 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 UL/DL 1 Indicates whether the PPDU is sent UL or DL. Set tothe value indicated by the TXVECTOR parameter UPLINK_FLAG. NOTE-The TDLSpeer can identify the TDLS frame by To DS and From DS fields in the MACheader of the MPDU. B1-B3 SIGB MCS 3 Indicates the MCS of the HE-SIG-Bfield: Set to 0 for MCS 0 Set to 1 for MCS 1 Set to 2 for MCS 2 Set to 3for MCS 3 Set to 4 for MCS 4 Set to 5 for MCS 5 The values 6 and 7 arereserved B4 SIGB DCM 1 Set to 1 indicates that the HE-SIG-B is modulatedwith DCM for the MCS. Set to 0 indicates that the HE-SIG-B is notmodulated with DCM for the MCS. NOTE-DCM is only applicable to MCS 0,MCS 1, MCS 3, and MCS 4. B5-B10 BSS Color 6 The BSS Color field is anidentifier of the BSS. Set to the value of the TXVECTOR parameterBSS_-COLOR. B11-B14 Spatial Reuse 4 Indicates whether or not spatialreuse is allowed during the transmission of this PPDU Set to the valueof the SPATIAL_REUSE parameter of the TXVECTOR, which contains a valuefrom Table 28-21 (Spatial Reuse field encoding for an HE SU PPDU, HE ERSU PPDU, and HE MU PPDU) (see 27.11.6 (SPATIAL_REUSE)). Set toSRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Setto SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 6 Number Bit Field of bits Description Two Parts of B15-B17Bandwidth 3 Set to 0 for 20 MHz. HE-SIG-A Set to 1 for 40 MHz. Set to 2for 80 MHz non-preamble puncturing mode. Set to 3 for 160 MHz and 80 +80 MHz non-preamble puncturing mode. If the SIGB Compression field is 0:Set to 4 for preamble puncturing in 80 MHz, where in the preamble onlythe secondary 20 MHz is punctured. Set to 5 for preamble puncturing in80 MHz, where in the preamble only one of the two 20 MHz sub- channelsin secondary 40 MHz is punctured. Set to 6 for preamble puncturing in160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble onlythe secondary 20 MHz is punctured. Set to 7 for preamble puncturing in160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble theprimary 40 MHz is present. If the SIGB Compression field is 1 thenvalues 4-7 are reserved. B18-B21 Number Of 4 If the HE-SIG-B Compressionfield is set to 0, indicates HE-SIG-B the number of OFDM symbols in theHE-SIG-B Symbols Or field: MU-MIMO Set to the number of OFDM symbols inthe HE-SIG-B Users field minus 1 if the number of OFDM symbols in theHE-SIG-B field is less than 16. Set to 15 to indicate that the number ofOFDM symbols in the HE-SIG-B field is equal to 16 if Longer Than 16 HESIG-B OFDM Symbols Support sub- field of the HE Capabilities elementtransmitted by at least one recipient STA is 0; Set to 15 to indicatethat the number of OFDM symbols in the HE-SIG-B field is greater than orequal to 16 if the Longer Than 16 HE SIG-B OFDM Symbols Support subfieldof the HE Capabilities element transmitted by all the recipient STAs are1 and if the HE-SIG-B data rate is less than MCS 4 without DCM. Theexact number of OFDM symbols in the HE-SIG-B field is calculated basedon the number of User fields in the HE-SIG-B content channel which isindicated by HE-SIG-B common field in this case. If the HE-SIG-BCompression field is set to 1, indicates the number of MU-MIMO users andis set to the number of NU-MIMO users minus 1 B22 SIGB 1 Set to 0 if theCommon field in HE-SIG-B is present. Compression Set to 1 if the Commonfield in HE-SIG-B is not present.

TABLE 7 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB23-B24 GI + LTF Size 2 Indicates the GI duration and HE-LTF size: Setto 0 to indicate a 4x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2xHE-LTF and 0.8 μs GI Set to 2 to indicate a 2x HE-LTF and 1.6 μs GI Setto 3 to indicate a 4x HE-LTF and 3.2 μs GI B25 Doppler 1 Set to 1 if oneof the following applies: The number of OFDM symbols in the Data fieldis larger than the signaled midamble periodicity plus 1 and the midambleis present The number of OFDM symbols in the Data field is less than orequal to the signaled midamble periodicity plus 1 (see 28.3.11.16Midamble), the midamble is not present, but the channel is fast varying.It recommends that midamble may be used for the PPDUs of the reverselink. Set to 0 otherwise. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicateno duration information if TXVECTOR parameter TXOP_DURATION is set toUNSPECIFIED. Set to a value less than 127 to indicate durationinformation for NAV setting and protection of the TXOP as follows: IfTXVECTOR parameter TXOP_DURATION is less than 512, then B0 is set to 0and B1-B6 is set to floor(TXOP_DURATION/8) Otherwise, B0 is set to 1 andB1-B6 is set to floor ((TXOP_DURATION − 512)/128) where B0 indicates theTXOP length granularity. Set to 0 for 8 μs; otherwise set to 1 for 128μs. B1-B6 indicates the scaled value of the TXOP_DURATION B7 Reserved 1Reserved and set to 1

TABLE 8 Number Bit Field of bits Description Two Parts of B8-B10 Numberof 3 If the Doppler field is set to 0, indicates the HE-SIG-A HE-LTFnumber of HE-LTF symbols: Symbols And Set to 0 for 1 HE-LTF symbolMidamble Set to 1 for 2 HE-LTF symbols Periodicity Set to 2 for 4 HE-LTFsymbols Set to 3 for 6 HE-LTF symbols Set to 4 for 8 HE-LTF symbolsOther values are reserved. If the Doppler field is set to 1 B8-B9indicates the number of HE-LTF symbols and B10 indicates midambleperiodicity: B8-B9 is encoded as follows: 0 indicates 1 HE-LTF symbol 1indicates 2 HE-LTF symbols 2 indicates 4 HE-LTF symbols 3 is reservedB10 is set to 0 if the TXVECTOR parameter MIDAMBLE_PERIODICITY is 10 andset to 1 if the TXVECTOR parameter PREAMBLE_PERIODICITY is 20. B11 LDPCExtra 1 Indication of the presence of the extra OFDM symbol Symbolsegment for LDPC. Segment Set to 1 if an extra OFDM symbol segment forLDPC is present. Set to 0 otherwise. B12 STBC 1 In an HE MU PPDU whereeach RU includes no more than 1 user, set to 1 to indicate all RUs areSTBC encoded in the payload, set to 0 to indicate all RUs are not STBCencoded in the payload. STBC does not apply to HE-SIG-B. STBC is notapplied if one or more RUs are used for MU-MIMO allocation. B13-B14Pre-FEC 2 Indicates the pre-FEC padding factor. Padding Set to 0 toindicate a pre-FEC padding factor of 4 Factor Set to 1 to indicate apre-FEC padding factor of 1 Set to 2 to indicate a pre-FEC paddingfactor of 2 Set to 3 to indicate a pre-FEC padding factor of 3 B15 PEDisambiguity 1 Indicates PE disambiguity as defined in 28.3.12 (Packetextension). B16-B19 CRC 4 CRC for bits 0-41 of the HE-SIG-A field (see28.3.10.7.3 (CRC computation)). Bits 0-41 of the HE-SIG-A fieldcorrespond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 ofHE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

In addition, the HE-SIG-A field of the HE TB PPDU may be defined asfollows.

TABLE 9 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU froman HE TB PPDU: Set to 0 for an HE TB PPDU B1-B6 BSS Color 6 The BSSColor field is an identifier of the BSS. Set to the value of theTXVECTOR parameter BSS_-COLOR. B7-B10 Spatial Reuse 1 4 Indicateswhether or not spatial reuse is allowed in a subband of the PPDU duringthe transmission of this PPDU, and if allowed, indicates a value that isused to determine a limit on the transmit power of a spatial reusetransmission. If the Bandwidth field indicates 20 MHz, 40 MHz, or 80 MHzthen this Spatial Reuse field applies to the first 20 MHz subband. Ifthe Bandwidth field indicates 160/80 + 80 MHz then this Spatial Reusefield applies to the first 40 MHz subband of the 160 MHz operating band.Set to the value of the SPATIAL_REUSE(1) parameter of the TXVECTOR,which contains a value from Table 28-22 (Spatial Reuse field encodingfor an HE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Setto SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU.Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 10 Number Bit Field of bits Description Two Parts of B11-B14Spatial Reuse 2 4 Indicates whether or not spatial reuse is allowed in aHE-SIG-A subband of the PPDU during the transmission of this PPDU, andif allowed, indicates a value that is used to determine a limit on thetransmit power of a spatial reuse transmission. If the Bandwidth fieldindicates 20 MHz, 40 MHz, or 80 MHz: This Spatial Reuse field applies tothe second 20 MHz subband. If the STA operating channel width is 20 MHz,then this field is set to the same value as Spatial Reuse 1 field. Ifthe STA operating channel width is 40 MHz in the 2.4 GHz band, thisfield is set to the same value as Spatial Reuse 1 field. If theBandwidth field indicates 160/80 + 80 MHz the this Spatial Reuse fieldapplies to the second 40 MHz subband of the 160 MHz operating band. Setto the value of the SPATIAL_REUSE(2) parameter of the TXVECTOR, whichcontains a value from Table 28-22 (Spatial Reuse field encoding for anHE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set toSRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Setto SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 11 Number Bit Field of bits Description Two Parts of B15-B18Spatial Reuse 3 4 Indicates whether or not spatial reuse is allowed in aHE-SIG-A subband of the PPDU during the transmission of this PPDU, andif allowed, indicates a value that is used to determine a limit on thetransmit power of a spatial reuse transmission. If the Bandwidth fieldindicates 20 MHz, 40 MHz or 80 MHz: This Spatial Reuse field applies tothe third 20 MHz subband. If the STA operating channel width is 20 MHzor 40 MHz, this field is set to the same value as Spatial Reuse 1 field.If the Bandwidth field indicates 160/80 + 80 MHz: This Spatial Reusefield applies to the third 40 MHz subband of the 160 MHz operating band.If the STA operating channel width is 80 + 80 MHz, this field is set tothe same value as Spatial Reuse 1 field. Set to the value of theSPATIAL_REUSE(3) parameter of the TXVECTOR, which contains a value fromTable 28-22 (Spatial Reuse field encoding for an HE TB PPDU) for an HETB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibitSRP-based spatial reuse during this PPDU. Set toSRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- based spatialreuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For theinterpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9(Spatial reuse operation).

TABLE 12 Number Bit Field of bits Description Two Parts of B19-B22Spatial Reuse 4 4 Indicates whether or not spatial reuse is allowed in aHE-SIG-A subband of the PPDU during the transmission of this PPDU, andif allowed, indicates a value that is used to determine a limit on thetransmit power of a spatial reuse transmission. If the Bandwidth fieldindicates 20 MHz, 40 MHz or 80 MHz: This Spatial Reuse field applies tothe fourth 20 MHz subband. If the STA operating channel width is 20 MHz,then this field is set to the same value as Spatial Reuse 1 field. Ifthe STA operating channel width is 40 MHz, then this field is set to thesame value as Spatial Reuse 2 field. If the Bandwidth field indicates160/80 + 80 MHz: This Spatial Reuse field applies to the fourth 40 MHzsubband of the 160 MHz operating band. If the STA operating channelwidth is 80 + 80 MHz, then this field is set to same value as SpatialReuse 2 field. Set to the value of the SPATIAL_REUSE(4) parameter of theTXVECTOR, which contains a value from Table 28-22 (Spatial Reuse fieldencoding for an HE TB PPDU) for an HE TB PPDU (see 27.11.6(SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-based spatialreuse during this PPDU. Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED toprohibit both SRP- based spatial reuse and non-SRG OBSS PD-based spatialreuse during this PPDU. For the interpretation of other values see27.11.6 (SPATIAL_REUSE) and 27.9 (Spatial reuse operation). B23 Reserved1 Reserved and set to 1. NOTE-Unlike other Reserved fields in HE-SIG-Aof the HE TB PPDU, B23 does not have a corresponding bit in the Triggerframe. B24-B25 Bandwidth 2 Set to 0 for 20 MHz Set to 1 for 40 MHz Setto 2 for 80 MHz Set to 3 for 160 MHz and 80 + 80 MHz

TABLE 13 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicate no duration information ifTXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED. Set to a valueless than 127 to indicate duration information for NAV setting andprotection of the TXOP as follows: If TXVECTOR parameter TXOP_DURATIONis less than 512, then B0 is set to 0 and B1-B6 is set tofloor(TXOP_DURATION/8) Otherwise, B0 is set to 1 and B1-B6 is set tofloor ((TXOP_DURATION − 512)/128) where B0 indicates the TXOP lengthgranularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6indicates the scaled value of the TXOP_DURATION B7-B15 Reserved 9Reserved and set to value indicated in the UL HE-SIG-A2 Reservedsubfield in the Trigger frame. B16-B19 CRC 4 CRC of bits 0-41 of theHE-SIG-A field. See 28.3.10.7.3 (CRC computation). Bits 0-41 of theHE-SIG-A field correspond to bits 0-25 of HE-SIG-A1 followed by bits0-15 of HE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

The HE-SIG-B 1240 may be included only for a multiple-user (MU) PPDU asdescribed above. Basically, the HE-SIG-A 1250 or the HE-SIG-B 1260 mayinclude resource allocation information (or virtual resource allocationinformation) for at least one receiving STA.

FIG. 13 illustrates an example of a PPDU used in the presentspecification.

The PPDU of FIG. 13 may be called in various terms such as an EHT PPDU,a TX PPDU, an RX PPDU, a first type or N-th type PPDU, or the like. Forexample, in the present specification, the PPDU or the EHT PPDU may becalled in various terms such as a TX PPDU, a RX PPDU, a first type orN-th type PPDU, or the like. In addition, the EHT PPDU may be used in anEHT system and/or a new WLAN system enhanced from the EHT system.

The PPDU of FIG. 13 may indicate the entirety or part of a PPDU typeused in the EHT system. For example, the example of FIG. 13 may be usedfor both of a single-user (SU) mode and a multi-user (MU) mode. In otherwords, the PPDU of FIG. 13 may be a PPDU for one receiving STA or aplurality of receiving STAs. When the PPDU of FIG. 13 is used for atrigger-based (TB) mode, the EHT-SIG of FIG. 13 may be omitted. In otherwords, a STA which has received a trigger frame for uplink-MU (UL-MU)may transmit the PPDU in which the EHT-SIG is omitted in the example ofFIG. 13 .

In FIG. 13 , an L-STF to an EHT-LTF may be called a preamble or aphysical preamble, and may begenerated/transmitted/received/obtained/decoded in a physical layer.

A subcarrier spacing of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, andEHT-SIG fields of FIG. 13 may be determined as 312.5 kHz, and asubcarrier spacing of the EHT-STF, EHT-LTF, and Data fields may bedetermined as 78.125 kHz. That is, a tone index (or subcarrier index) ofthe L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields may beexpressed in unit of 312.5 kHz, and a tone index (or subcarrier index)of the EHT-STF, EHT-LTF, and Data fields may be expressed in unit of78.125 kHz.

In the PPDU of FIG. 13 , the L-LTE and the L-STF may be the same asthose in the conventional fields.

The L-SIG field of FIG. 13 may include, for example, bit information of24 bits. For example, the 24-bit information may include a rate field of4 bits, a reserved bit of 1 bit, a length field of 12 bits, a parity bitof 1 bit, and a tail bit of 6 bits. For example, the length field of 12bits may include information related to a length or time duration of aPPDU. For example, the length field of 12 bits may be determined basedon a type of the PPDU. For example, when the PPDU is a non-HT, HT, VHTPPDU or an EHT PPDU, a value of the length field may be determined as amultiple of 3. For example, when the PPDU is an HE PPDU, the value ofthe length field may be determined as “a multiple of 3”+1 or “a multipleof 3”+2. In other words, for the non-HT, HT, VHT PPDI or the EHT PPDU,the value of the length field may be determined as a multiple of 3, andfor the HE PPDU, the value of the length field may be determined as “amultiple of 3”+1 or “a multiple of 3”+2.

For example, the transmitting STA may apply BCC encoding based on a ½coding rate to the 24-bit information of the L-SIG field. Thereafter,the transmitting STA may obtain a BCC coding bit of 48 bits. BPSKmodulation may be applied to the 48-bit coding bit, thereby generating48 BPSK symbols. The transmitting STA may map the 48 BPSK symbols topositions except for a pilot subcarrier{subcarrier index −21, −7, +7,+21} and a DC subcarrier{subcarrier index 0}. As a result, the 48 BPSKsymbols may be mapped to subcarrier indices −26 to −22, −20 to −8, −6 to−1, +1 to +6, +8 to +20, and +22 to +26. The transmitting STA mayadditionally map a signal of {−1, −1, −1, 1} to a subcarrier index{−28,−27, +27, +28}. The aforementioned signal may be used for channelestimation on a frequency domain corresponding to {−28, −27, +27, +28}.

The transmitting STA may generate an RL-SIG generated in the same manneras the L-SIG. BPSK modulation may be applied to the RL-SIG. Thereceiving STA may know that the RX PPDU is the HE PPDU or the EHT PPDU,based on the presence of the RL-SIG.

A universal SIG (U-SIG) may be inserted after the RL-SIG of FIG. 13 .The U-SIB may be called in various terms such as a first SIG field, afirst SIG, a first type SIG, a control signal, a control signal field, afirst (type) control signal, or the like.

The U-SIG may include information of N bits, and may include informationfor identifying a type of the EHT PPDU. For example, the U-SIG may beconfigured based on two symbols (e.g., two contiguous OFDM symbols).Each symbol (e.g., OFDM symbol) for the U-SIG may have a duration of 4us. Each symbol of the U-SIG may be used to transmit the 26-bitinformation. For example, each symbol of the U-SIG may betransmitted/received based on 52 data tomes and 4 pilot tones.

Through the U-SIG (or U-SIG field), for example, A-bit information(e.g., 52 un-coded bits) may be transmitted. A first symbol of the U-SIGmay transmit first X-bit information (e.g., 26 un-coded bits) of theA-bit information, and a second symbol of the U-SIB may transmit theremaining Y-bit information (e.g., 26 un-coded bits) of the A-bitinformation. For example, the transmitting STA may obtain 26 un-codedbits included in each U-SIG symbol. The transmitting STA may performconvolutional encoding (i.e., BCC encoding) based on a rate of R=½ togenerate 52-coded bits, and may perform interleaving on the 52-codedbits. The transmitting STA may perform BPSK modulation on theinterleaved 52-coded bits to generate 52 BPSK symbols to be allocated toeach U-SIG symbol. One U-SIG symbol may be transmitted based on 65 tones(subcarriers) from a subcarrier index −28 to a subcarrier index +28,except for a DC index 0. The 52 BPSK symbols generated by thetransmitting STA may be transmitted based on the remaining tones(subcarriers) except for pilot tones, i.e., tones −21, −7, +7, +21.

For example, the A-bit information (e.g., 52 un-coded bits) generated bythe U-SIG may include a CRC field (e.g., a field having a length of 4bits) and a tail field (e.g., a field having a length of 6 bits). TheCRC field and the tail field may be transmitted through the secondsymbol of the U-SIG. The CRC field may be generated based on 26 bitsallocated to the first symbol of the U-SIG and the remaining 16 bitsexcept for the CRC/tail fields in the second symbol, and may begenerated based on the conventional CRC calculation algorithm. Inaddition, the tail field may be used to terminate trellis of aconvolutional decoder, and may be set to, for example, “000000”.

The A-bit information (e.g., 52 un-coded bits) transmitted by the U-SIG(or U-SIG field) may be divided into version-independent bits andversion-dependent bits. For example, the version-independent bits mayhave a fixed or variable size. For example, the version-independent bitsmay be allocated only to the first symbol of the U-SIG, or theversion-independent bits may be allocated to both of the first andsecond symbols of the U-SIG. For example, the version-independent bitsand the version-dependent bits may be called in various terms such as afirst control bit, a second control bit, or the like.

For example, the version-independent bits of the U-SIG may include a PHYversion identifier of 3 bits. For example, the PHY version identifier of3 bits may include information related to a PHY version of a TX/RX PPDU.For example, a first value of the PHY version identifier of 3 bits mayindicate that the TX/RX PPDU is an EHT PPDU. In other words, when thetransmitting STA transmits the EHT PPDU, the PHY version identifier of 3bits may be set to a first value. In other words, the receiving STA maydetermine that the RX PPDU is the EHT PPDU, based on the PHY versionidentifier having the first value.

For example, the version-independent bits of the U-SIG may include aUL/DL flag field of 1 bit. A first value of the UL/DL flag field of 1bit relates to UL communication, and a second value of the UL/DL flagfield relates to DL communication.

For example, the version-independent bits of the U-SIG may includeinformation related to a TXOP length and information related to a BSScolor ID.

For example, when the EHT PPDU is divided into various types (e.g.,various types such as an EHT PPDU related to an SU mode, an EHT PPDUrelated to a MU mode, an EHT PPDU related to a TB mode, an EHT PPDUrelated to extended range transmission, or the like), informationrelated to the type of the EHT PPDU may be included in theversion-dependent bits of the U-SIG.

For example, the U-SIG may include: 1) a bandwidth field includinginformation related to a bandwidth; 2) a field including informationrelated to an MCS scheme applied to EHT-SIG; 3) an indication fieldincluding information regarding whether a dual subcarrier modulation(DCM) scheme is applied to EHT-SIG; 4) a field including informationrelated to the number of symbol used for EHT-SIG; 5) a field includinginformation regarding whether the EHT-SIG is generated across a fullband; 6) a field including information related to a type of EHT-LTF/STF;and 7) information related to a field indicating an EHT-LTF length and aCP length.

Preamble puncturing may be applied to the PPDU of FIG. 13 . The preamblepuncturing implies that puncturing is applied to part (e.g., a secondary20 MHz band) of the full band. For example, when an 80 MHz PPDU istransmitted, a STA may apply puncturing to the secondary 20 MHz band outof the 80 MHz band, and may transmit a PPDU only through a primary 20MHz band and a secondary 40 MHz band.

For example, a pattern of the preamble puncturing may be configured inadvance. For example, when a first puncturing pattern is applied,puncturing may be applied only to the secondary 20 MHz band within the80 MHz band. For example, when a second puncturing pattern is applied,puncturing may be applied to only any one of two secondary 20 MHz bandsincluded in the secondary 40 MHz band within the 80 MHz band. Forexample, when a third puncturing pattern is applied, puncturing may beapplied to only the secondary 20 MHz band included in the primary 80 MHzband within the 160 MHz band (or 80+80 MHz band). For example, when afourth puncturing is applied, puncturing may be applied to at least one20 MHz channel not belonging to a primary 40 MHz band in the presence ofthe primary 40 MHz band included in the 80 MHaz band within the 160 MHzband (or 80+80 MHz band).

Information related to the preamble puncturing applied to the PPDU maybe included in U-SIG and/or EHT-SIG. For example, a first field of theU-SIG may include information related to a contiguous bandwidth, andsecond field of the U-SIG may include information related to thepreamble puncturing applied to the PPDU.

For example, the U-SIG and the EHT-SIG may include the informationrelated to the preamble puncturing, based on the following method. Whena bandwidth of the PPDU exceeds 80 MHz, the U-SIG may be configuredindividually in unit of 80 MHz. For example, when the bandwidth of thePPDU is 160 MHz, the PPDU may include a first U-SIG for a first 80 MHzband and a second U-SIG for a second 80 MHz band. In this case, a firstfield of the first U-SIG may include information related to a 160 MHzbandwidth, and a second field of the first U-SIG may include informationrelated to a preamble puncturing (i.e., information related to apreamble puncturing pattern) applied to the first 80 MHz band. Inaddition, a first field of the second U-SIG may include informationrelated to a 160 MHz bandwidth, and a second field of the second U-SIGmay include information related to a preamble puncturing (i.e.,information related to a preamble puncturing pattern) applied to thesecond 80 MHz band. Meanwhile, an EHT-SIG contiguous to the first U-SIGmay include information related to a preamble puncturing applied to thesecond 80 MHz band (i.e., information related to a preamble puncturingpattern), and an EHT-SIG contiguous to the second U-SIG may includeinformation related to a preamble puncturing (i.e., information relatedto a preamble puncturing pattern) applied to the first 80 MHz band.

Additionally or alternatively, the U-SIG and the EHT-SIG may include theinformation related to the preamble puncturing, based on the followingmethod. The U-SIG may include information related to a preamblepuncturing (i.e., information related to a preamble puncturing pattern)for all bands. That is, the EHT-SIG may not include the informationrelated to the preamble puncturing, and only the U-SIG may include theinformation related to the preamble puncturing (i.e., the informationrelated to the preamble puncturing pattern).

The U-SIG may be configured in unit of 20 MHz. For example, when an 80MHz PPDU is configured, the U-SIG may be duplicated. That is, fouridentical U-SIGs may be included in the 80 MHz PPDU. PPDUs exceeding an80 MHz bandwidth may include different U-SIGs.

The EHT-SIG of FIG. 13 may include control information for the receivingSTA. The EHT-SIG may be transmitted through at least one symbol, and onesymbol may have a length of 4 us. Information related to the number ofsymbols used for the EHT-SIG may be included in the U-SIG.

The PPDU of FIG. 13 may be determined (or identified) as an EHT PPDUbased on the following method.

A receiving STA may determine a type of an RX PPDU as the EHT PPDU,based on the following aspect. For example, the RX PPDU may bedetermined as the EHT PPDU: 1) when a first symbol after an L-LTF signalof the RX PPDU is a BPSK symbol; 2) when RL-SIG in which the L-SIG ofthe RX PPDU is repeated is detected; and 3) when a result of applying“modulo 3” to a value of a length field of the L-SIG of the RX PPDU isdetected as “0”. When the RX PPDU is determined as the EHT PPDU, thereceiving STA may detect a type of the EHT PPDU (e.g., anSU/MU/Trigger-based/Extended Range type), based on bit informationincluded in a symbol after the RL-SIG of FIG. 13 . In other words, thereceiving STA may determine the RX PPDU as the EHT PPDU, based on: 1) afirst symbol after an L-LTF signal, which is a BPSK symbol; 2) RL-SIGcontiguous to the L-SIG field and identical to L-SIG; 3) L-SIG includinga length field in which a result of applying “modulo 3” is set to “0”;and 4) a 3-bit PHY version identifier of the aforementioned U-SIG (e.g.,a PHY version identifier having a first value).

For example, the receiving STA may determine the type of the RX PPDU asthe HE PPDU, based on the following aspect. For example, the RX PPDU maybe determined as the HE PPDU: 1) when a first symbol after an L-LTFsignal is a BPSK symbol; 2) when RL-SIG in which the L-SIG is repeatedis detected; and 3) when a result of applying “modulo 3” to a value of alength field of the L-SIG is detected as “1” or “2”.

For example, the receiving STA may determine the type of the RX PPDU asa non-HT, HT, and VHT PPDU, based on the following aspect. For example,the RX PPDU may be determined as the non-HT, HT, and VHT PPDU: 1) when afirst symbol after an L-LTF signal is a BPSK symbol; and 2) when RL-SIGin which L-SIG is repeated is not detected. In addition, even if thereceiving STA detects that the RL-SIG is repeated, when a result ofapplying “modulo 3” to the length value of the L-SIG is detected as “0”,the RX PPDU may be determined as the non-HT, HT, and VHT PPDU.

In the following example, a signal represented as a (TX/RX/UL/DL)signal, a (TX/RX/UL/DL) frame, a (TX/RX/UL/DL) packet, a (TX/RX/UL/DL)data unit, (TX/RX/UL/DL) data, or the like may be a signaltransmitted/received based on the PPDU of FIG. 13 . The PPDU of FIG. 13may be used to transmit/receive frames of various types. For example,the PPDU of FIG. 13 may be used for a control frame. An example of thecontrol frame may include a request to send (RTS), a clear to send(CTS), a power save-poll (PS-poll), BlockACKReq, BlockAck, a null datapacket (NDP) announcement, and a trigger frame. For example, the PPDU ofFIG. 13 may be used for a management frame. An example of the managementframe may include a beacon frame, a (re-)association request frame, a(re-)association response frame, a probe request frame, and a proberesponse frame. For example, the PPDU of FIG. 13 may be used for a dataframe. For example, the PPDU of FIG. 13 may be used to simultaneouslytransmit at least two or more of the control frame, the managementframe, and the data frame.

FIG. 14 illustrates an example of a modified transmission device and/orreceiving device of the present specification.

Each device/STA of the sub-figure (a)/(b) of FIG. 1 may be modified asshown in FIG. 14 . A transceiver 630 of FIG. 14 may be identical to thetransceivers 113 and 123 of FIG. 1 . The transceiver 630 of FIG. 14 mayinclude a receiver and a transmitter.

A processor 610 of FIG. 14 may be identical to the processors 111 and121 of FIG. 1 . Alternatively, the processor 610 of FIG. 14 may beidentical to the processing chips 114 and 124 of FIG. 1 .

A memory 620 of FIG. 14 may be identical to the memories 112 and 122 ofFIG. 1 . Alternatively, the memory 620 of FIG. 14 may be a separateexternal memory different from the memories 112 and 122 of FIG. 1 .

Referring to FIG. 14 , a power management module 611 manages power forthe processor 610 and/or the transceiver 630. A battery 612 suppliespower to the power management module 611. A display 613 outputs a resultprocessed by the processor 610. A keypad 614 receives inputs to be usedby the processor 610. The keypad 614 may be displayed on the display613. A SIM card 615 may be an integrated circuit which is used tosecurely store an international mobile subscriber identity (IMSI) andits related key, which are used to identify and authenticate subscriberson mobile telephony devices such as mobile phones and computers.

Referring to FIG. 14 , a speaker 640 may output a result related to asound processed by the processor 610. A microphone 641 may receive aninput related to a sound to be used by the processor 610.

Hereinafter, technical features of channel bonding supported by the STAof the present disclosure will be described.

For example, in an IEEE 802.11n system, 40 MHz channel bonding may beperformed by combining two 20 MHz channels. In addition, 40/80/160 MHzchannel bonding may be performed in the IEEE 802.11ac system.

For example, the STA may perform channel bonding for a primary 20 MHzchannel (P20 channel) and a secondary 20 MHz channel (S20 channel). Abackoff count/counter may be used in the channel bonding process. Thebackoff count value may be chosen as a random value and decrementedduring the backoff interval. In general, when the backoff count valuebecomes 0, the STA may attempt to access the channel.

During the backoff interval, when the P20 channel is determined to be inthe idle state and the backoff count value for the P20 channel becomes0, the STA, performing channel bonding, determines whether an S20channel has maintained an idle state for a certain period of time (forexample, point coordination function interframe space (PIFS)). If theS20 channel is in an idle state, the STA may perform bonding on the P20channel and the S20 channel. That is, the STA may transmit a signal(PPDU) through a 40 MHz channel (that is, a 40 MHz bonding channel)including a P20 channel and the S20 channel.

FIG. 15 illustrates an example of channel bonding. As shown in FIG. 15 ,the primary 20 MHz channel and the secondary 20 MHz channel may make upa 40 MHz channel (primary 40 MHz channel) through channel bonding. Thatis, the bonded 40 MHz channel may include a primary 20 MHz channel and asecondary 20 MHz channel.

Channel bonding may be performed when a channel contiguous to theprimary channel is in an idle state. That is, the Primary 20 MHzchannel, the Secondary 20 MHz channel, the Secondary 40 MHz channel, andthe Secondary 80 MHz channel can be sequentially bonded. However, if thesecondary 20 MHz channel is determined to be in the busy state, channelbonding may not be performed even if all other secondary channels are inthe idle state. In addition, when it is determined that the secondary 20MHz channel is in the idle state and the secondary 40 MHz channel is inthe busy state, channel bonding may be performed only on the primary 20MHz channel and the secondary 20 MHz channel.

Hereinafter, preamble puncturing supported by a STA in the presentdisclosure will be described.

For example, in the example of FIG. 15 , if the Primary 20 MHz channel,the Secondary 40 MHz channel, and the Secondary 80 MHz channel are allin the idle state, but the Secondary 20 MHz channel is in the busystate, bonding to the secondary 40 MHz channel and the secondary 80 MHzchannel may not be possible. In this case, the STA may configure a 160MHz PPDU and may perform a preamble puncturing on the preambletransmitted through the secondary 20 MHz channel (for example, L-STF,L-LTF, L-SIG, RL-SIG, U-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF,EHT-SIG, EHT-STF, EHT-LTF, etc.), so that the STA may transmit a signalthrough a channel in the idle state. In other words, the STA may performpreamble puncturing for some bands of the PPDU. Information on preamblepuncturing (for example, information about 20/40/80 MHz channels/bandsto which puncturing is applied) may be included in a signal field (forexample, HE-SIG-A, U-SIG, EHT-SIG) of the PPDU.

Hereinafter, technical features of a multi-link (ML) supported by a STAof the present disclosure will be described.

The STA (AP and/or non-AP STA) of the present disclosure may supportmulti-link (ML) communication. ML communication may refer tocommunication supporting a plurality of links. The link related to MLcommunication may include channels of the 2.4 GHz band shown in FIG. 9 ,the 5 GHz band shown in FIG. 10 , and the 6 GHz band shown in FIG. 11(for example, 20/40/80/160/240/320 MHz channels).

A plurality of links used for ML communication may be set in variousways. For example, a plurality of links supported by one STA for MLcommunication may be a plurality of channels in a 2.4 GHz band, aplurality of channels in a 5 GHz band, and a plurality of channels in a6 GHz band. Alternatively, a plurality of links supported by one STA forML communication may be a combination of at least one channel in the 2.4GHz band (or 5 GHz/6 GHz band) and at least one channel in the 5 GHzband (or 2.4 GHz/6 GHz band). Meanwhile, at least one of the pluralityof links supported by one STA for ML communication may be a channel towhich preamble puncturing is applied.

The STA may perform an ML setup to perform ML communication. The MLsetup may be performed based on a management frame or control frame suchas a Beacon, a Probe Request/Response, an Association Request/Response,and the like. For example, information about ML setup may be included inan element field included in a Beacon, a Probe Request/Response, anAssociation Request/Response, and the like.

When ML setup is completed, an enabled link for ML communication may bedetermined. The STA may perform frame exchange through at least one of aplurality of links determined as an enabled link. For example, theenabled link may be used for at least one of a management frame, acontrol frame, and a data frame.

When one STA supports multiple links, a transceiver supporting each linkmay operate as one logical STA. For example, one STA supporting twolinks may be expressed as one Multi Link Device (MLD) including a firstSTA for the first link and a second STA for the second link. Forexample, one AP supporting two links may be expressed as one AP MLDincluding a first AP for a first link and a second AP for a second link.In addition, one non-AP supporting two links may be expressed as onenon-AP MLD including a first STA for the first link and a second STA forthe second link.

Hereinafter, more specific features related to the ML setup aredescribed.

The MLD (AP MLD and/or non-AP MLD) may transmit, through ML setup,information on a link that the corresponding MLD can support. Linkinformation may be configured in various ways. For example, informationon the link may include at least one of 1) information on whether theMLD (or STA) supports simultaneous RX/TX operation, 2) information onthe number/upper limit of uplink/downlink links supported by the MLD (orSTA), 3) information on the location/band/resource of theuplink/downlink Link supported by the MLD (or STA), 4) information onthe frame type (management, control, data, etc.) available or preferredin at least one uplink/downlink link, 5) information on ACK policyavailable or preferred in at least one uplink/downlink link, and 6)information on an available or preferred traffic identifier (TID) in atleast one uplink/downlink Link. The TID is related to the priority oftraffic data and is expressed as eight types of values according to theconventional wireless LAN standard. That is, eight TID valuescorresponding to four access categories (ACs) (AC_Background (AC_BK),AC_Best Effort (AC_BE), AC_Video (AC_VI), AC_Voice (AC_VO)) according tothe conventional WLAN standard may be defined.

For example, it may be preset that all TIDs are mapped foruplink/downlink link. Specifically, if negotiation is not made throughML setup, if all TIDs are used for ML communication, and if the mappingbetween uplink/downlink link and TID is negotiated through additional MLsettings, the negotiated TID may be used for ML communication.

Through ML setup, a plurality of links usable by the transmitting MLDand the receiving MLD related to ML communication may be set, and thismay be referred to as an “enabled link”. The “enabled link” may becalled differently in various expressions. For example, it may bereferred to as various expressions such as a first link, a second link,a transmission link, and a reception link.

After the ML setup is completed, the MLD could update the ML setup. Forexample, the MLD may transmit information on a new link when it isnecessary to update information on the link. Information on the new linkmay be transmitted based on at least one of a management frame, acontrol frame, and a data frame.

According to an embodiment, the MLD may include a non-AP MLD and anAP-MLD. The non-AP MLD and the AP-MLD may be classified according to thefunction of an access point (AP). The non-AP MLD and the AP-MLD may bephysically separated or logically separated. For example, when the MLDperforms an AP function, it may be referred to as an AP MLD, and whenthe MLD performs an STA function, it may be referred to as a non-AP MLD.

In the following specification, the MLD has one or moreconnected/associated STAs and has one MAC service access point (SAP)through an upper link layer (Logical Link Control, LLC). The MLD maymean a physical device or a logical device. Hereinafter, a device maymean the MLD.

In addition, the MLD may include at least one STA connected to each linkof the multi-link. For example, the processor of the MLD may control theat least one STA. For example, the at least one STA may be independentlyconfigured and operated. The at least one STA may include a processorand a transceiver, respectively. For example, the at least one STA mayoperate independently regardless of the processor of the MLD.

In the following specification, for the convenience of description, itis described that the MLD (or the processor of the MLD) controls atleast one STA, but is not limited thereto. As described above, the atleast one STA may transmit/receive a signal independently regardless ofthe MLD.

According to an embodiment, the AP MLD or the non-AP MLD may beconfigured in a structure having a plurality of links. In other words,the non-AP MLD may support a plurality of links. The non-AP MLD mayinclude a plurality of STAs. Each of a plurality of STAs may have a linkfor a corresponding STA.

In the EHT standard (802.11be standard), a Multi-Link Device (MLD)structure in which one AP/non-AP MLD supports multiple links isconsidered as a major feature. STA(s) included in the non-AP MLD maytransmit information related to other STAs in the same non-AP MLDthrough one link. Accordingly, there is an effect that the overhead offrame exchange is reduced. In addition, there is an effect of increasingthe link usage efficiency of the STA and reducing power consumption.

FIG. 16 illustrates an example of the structure of a non-AP MLD.

Referring to FIG. 16 , the non-AP MLD may be configured in a structurehaving a plurality of links. In other words, the non-AP MLD may supportthe plurality of links. The non-AP MLD may include a plurality of STAs.The plurality of STAs may have a link for each STA. Although FIG. 16shows an example of the structure of the non-AP MLD, the structure of anAP MLD may be configured the same as the example of the structure of thenon-AP MLD illustrated in FIG. 16 .

For example, the non-AP MLD may include STA 1, STA 2, and STA 3. STA 1may operate on link 1. Link 1 may be included in a 5 GHz band. STA 2 mayoperate on link 2. Link 2 may be included in a 6 GHz band. STA 3 mayoperate on link 3. Link 3 may be included in the 5 GHz band. The bandsincluding link 1/2/3 are provided for illustration, and link 1/2/3 maybe included in 2.4, 5, and 6 GHz.

An AP/non-AP MLD supporting a multi-link, each AP of the AP MLD and eachSTA of the non-AP MLD may be connected to each link through a link setupprocess. The connected link may be changed to another link or bereconnected by the AP MLD or the non-AP MLD depending on a situation.

In the EHT standard, to reduce power consumption, links may be dividedinto an anchored link or a non-anchored link. The anchored link or thenon-anchored link may be called variously. For example, the anchoredlink may be referred to as a primary link. The non-anchored link may bereferred to as a secondary link.

According to an embodiment, the AP MLD supporting the multi-link maymange each link by designating each link as an anchored link or anon-anchored link. The AP MLD may support one or more links among aplurality of links as anchored links. The non-AP MLD may select and useone or more anchored links thereof from an anchored link list (a list ofanchored links supported by the AP MLD).

For example, the anchored link may be used not only for a frame exchangefor synchronization but also for a non-data frame exchange (i.e., abeacon and management frame exchange). The non-anchored link may be usedonly for a data frame exchange.

The non-AP MLD may watch (or monitor) only the anchored link to receivea beacon and a management frame during an idle period. Therefore, thenon-AP MLD needs to be connected to at least one anchored link toreceive a beacon and a management frame. The one or more anchored linksneed to always maintain an enabled state. However, the non-anchored linkis used only for a data frame exchange. Therefore, a STA correspondingto the non-anchored link (or a STA connected to the non-anchored link)may enter a doze during the idle period in which the channel/link is notused. Accordingly, it is possible to reduce power consumption.

In the following specification, a protocol for the AP MLD or the non-APMLD to dynamically recommend or request a link reconnection according toa situation for an efficient link connection may be proposed. Further,in the following specification, an anchored link reconnection protocolin consideration of a characteristic of an anchored link used for powerreduction as well as a general link may be additionally proposed.

Embodiment for Link Change and Reconnection

According to an embodiment, each link between the AP MLD and the non-APMLD may be determined in an association or (re)association process. TheAP MLD and the non-AP MLD may perform a frame exchange through theconnected link. A specific embodiment in which the AP MLD and the non-APMLD are connected through a link setup process may be described withreference to FIG. 17 .

FIG. 17 illustrates an example in which the AP MLD and the non-AP MLDare connected through a link setup process.

Referring to FIG. 17 , the AP MLD may include AP 1, AP 2, and AP 3. Thenon-AP MLD may include STA 1 and STA 2. AP 1 and STA 1 may be connectedthrough link 1. AP 2 and STA 2 may be connected through link 2.

For example, AP 1 and STA 1 may be connected through link 1 through afirst link setup process. AP 2 and STA 2 may be connected through link 2through a second link setup process. In another example, the AP MLD andthe non-AP MLD may be connected through a single link setup process. Inother words, the AP MLD and the non-AP MLD may be connected through link1 and link 2 based on the single link setup process.

As described above, each AP and each STA may perform a frame exchangethrough a connected link. In addition, through one link, information onother APs related to a different link or other STAs related to thedifferent link may be transmitted and received.

However, after this link setup process, the AP MLD or the non-AP MLD mayrequest a link change or reconnection for a more efficient frameexchange (e.g., load balancing or interference avoiding) depending on asituation/environment.

An embodiment related to a link change or reconnection may be describedwith reference to FIG. 18 .

FIG. 18 illustrates an example in which a link is changed orreconnected.

Referring to FIG. 18 , STA 2 is conventionally connected to AP 2.Subsequently, excessive data loads may be generated in AP 2. STA 2 maybe reconnected to AP 3 with a relatively small data load. In this case,the AP MLD and the non-AP MLD may perform an efficient data exchange.

FIG. 19 illustrates a specific example in which a link is changed orreconnected.

Referring to FIG. 19 , AP 1 of the AP MLD may be connected to STA 1 ofthe non-AP MLD through link 1. AP 2 of the AP MLD may be connected toSTA 2 of the non-AP MLD through link 2. Subsequently, STA 2 mayattempt/request a connection to AP 3 through a link change orreconnection, and STA 2 may be connected to AP 3 through link 2 based onthe link change or reconnection.

According to an embodiment, the non-AP MLD and the AP MLD may request alink transition to improve performance. The AP MLD and the non-AP MLDmay transmit/receive/exchange various pieces of information on eachcurrent link and information on a link state. Accordingly, the AP MLDand the non-AP MLD may select a link more suitable for transmitting andreceiving a signal based on the various pieces of information on eachcurrent link and the link state, and may transmit the foregoinginformation to help the selection. For example, the various pieces ofinformation on each current link may include information on a datatraffic load for each link and a channel access capability betweenlinks. For example, the link state may be set to “disabled” or“enabled”.

In the following specification, a process in which the AP MLD/non-AP MLDnegotiates with the non-AP MLD/AP MLD to request a change orreconnection to a link other than the connected link to improveperformance may be referred to as a “link switching negotiation”. The“link switching negotiation” may be referred to as various terms, andmay be changed.

In the link switching negotiation process, the non-AP MLD (or AP MLD)may make a request to change a link connected to a specific STA toanother link, and the AP MLD (or non-AP MLD) may respond to this requestusing a request acceptance or rejection message.

For example, as illustrated in FIG. 19 , when a link change is agreed onthrough a link switching negotiation, the STA may perform a linkre-setup process of being reconnected by changing the existing link fromAP 2 to AP 3.

In the following description, link change or reconnection processes maybe divided into those when requested by the AP MLD and when requested bythe non-AP MLD.

Embodiment in which AP MLD Requests Link Change or Reconnection

According to an embodiment, the AP MLD may request a link change orreconnection from the non-AP MLD for efficient data transmission. Forexample, for load balancing, the AP MLD may request a STA to change orreconnect to a more efficient link based on data traffic of each AP.

For example, the AP MLD may calculate/identify/determine a link suitablefor STAs of the non-AP MLD based on data traffic load information oneach AP and/or channel access capability information on each link (e.g.,information on a simultaneous TX/RX (STR) capability). Subsequently, theAP MLD may request a link change or reconnection from a STA (or non-APMLD) based on the data traffic load information on each AP and/or thechannel access capability information on each link.

As described above, when requesting the link change, the AP MLD maytransmit information on a link considered to be most suitable to thenon-AP MLD through a request message. For example, the request messagemay include a beacon or a management frame.

In relation to the foregoing embodiment, an element or field includingthe information on the link considered to be most suitable may be newlyproposed. The newly proposed element or field may be defined as a“recommended link”. The “recommended link” is provided for illustration,and a specific element or field name may be changed.

Recommend link (element/field): An element or field for the AP MLD torecommend a link most suitable for the STA of the non-AP MLD based onvarious pieces of information on each link (e.g., a data load for eachlink). For example, the recommend link (element/field) may be indicatedas link ID information or AP BSS information of the AP MLD. In otherwords, the recommend link (element/field) may include the link IDinformation or the AP BSS information of the AP MLD.

According to an embodiment, the recommend link (element/field) may beoptionally included in a link switching response and transmitted. Forexample, the STA may establish a connection to the link recommended bythe AP based on the element/field (i.e., the recommend link). In anotherexample, the STA may request a connection to a link different from theindicated link based on the element/field (i.e., the recommend Link) andadditional information possessed by the STA.

A specific signal exchange process between the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 20 .

FIG. 20 illustrates the operations of the AP MLD and the non-AP MLD forthe link change or reconnection.

Referring to FIG. 20 , in a situation in which STA 2 is connected to AP2 through link 2, enormous data traffic may be concentrated in AP 2. Inother words, in the situation in which the STA 2 is connected to the AP2 through link 2, enormous data traffic may be generated in the AP 2.

The AP MLD (or AP 2) may request the non-AP MLD (or STA 2) to reconnectto AP 3 which has relatively few STA connections. A message forrequesting a reconnection is generally transmitted to a STA (i.e., STA2) that wants to reconnect, but may be transmitted to any STA (i.e.,other STAs) depending on a situation (e.g., a channel state or linkstate). In other words, a STA to which the request message forrequesting a reconnection (e.g., a link switching request frame) istransmitted may be changed based on the channel state or the link state.

For example, the STA (i.e., STA 2) having received the request messagefor requesting the reconnection may transmit a response message of“Accept” (e.g., a link switching response frame) when accepting therequest. In another example, when the STA (i.e., STA 2) may transmit aresponse message of “Decline” when rejecting the request.

In general, the STA (i.e., STA 2) accepting the reconnection transmitthe response message via the existing link (the connected link beforethe reconnection), but the response message may also be transmittedthrough any link (i.e., another STA) by using a characteristic of themulti-link.

When STA 2 accepts a link reconnection request, STA 2 may bedisconnected from existing AP 2 and may request a link reconnection toAP 3 after transmitting a response message. Here, a reconnection requestprocess may be performed in the same manner as the existing link setupprocess between the MLDs. After a link setup process between AP 3 andSTA 2 is completed, STA 2 may perform a frame exchange with AP 3 throughlink 2.

However, when STA 2 rejects the link reconnection request, STA 2 and AP2 may use the existing connected link (i.e., link 2) as it is.

According to an embodiment, when the AP recommends a suitable link whenrequesting a link change from the STA, the STA may or may not change thelink to the recommended link. For example, the AP may use the foregoingrecommend link to recommend the link suitable for the STA.

For example, the STA may accept the link change via the response messageto the request message for requesting the reconnection from the AP. TheSTA may accept/identify the link change via the recommended link, andmay request another link change from the AP based on information otherthan information included in the request message.

Accordingly, the AP needs to notify the STA of whether to accept theresponse message. To this end, the AP may transmit a confirmationmessage (e.g., a link switching confirmation frame) to the STA inresponse to the response message (e.g., the link switching responseframe) from the STA.

Specific operations of the AP MLD and the non-AP MLD of the foregoingembodiment may be described with reference to FIG. 21 .

FIG. 21 illustrates the operations of the AP MLD and the non-AP MLD fora link change or reconnection.

Referring to FIG. 21 , AP 2 may request a link change includingrecommended link information from STA 2. In other words, AP 2 maytransmit a link switching request frame including the recommended linkinformation to STA 2.

STA 2 may transmit whether to accept a link request through a linkswitching response frame.

For example, when accepting link switching, STA 2 may transmit the linkswitching response frame link including information on a link to bechanged. Here, the information on the link to be changed may or may notbe the same as a recommended link.

In another example, when STA 2 responds with the link switching responseframe by selecting a link other than the recommended link provided by AP2, the AP may transmit a message with respect to whether to finallyaccept the link to the STA. The message may be referred to as a linkswitching confirmation frame.

For example, AP 2 may accept the link change to the link designated bySTA 2 through the link switching confirmation frame. STA 2 may attemptthe link change to the link designated by STA 2 based on the linkswitching confirmation frame.

In another example, AP 2 may reject the link change to the linkdesignated by STA 2 through the link switching confirmation frame. STA 2and AP 2 may maintain a connection via the existing connected linkwithout changing the link.

The embodiment illustrated in FIG. 21 may be applied even when the APtransmits the link switching request frame without including therecommended link information. For example, when the AP (e.g., AP 2)transmits a link switching request frame to the STA (e.g., STA 2)without recommended link information, the STA may directly designate alink to be changed based on pieces of information possessed by the STA,and may respond to the AP with a link switching response frame. Even inthis case, the AP needs to finally transmit a link switchingconfirmation frame for acceptance. Accordingly, an embodiment in whichthe AP transmits a link switching confirmation frame may be applied evenwhen recommended link information is not included in link switchingrequest frame.

Embodiment in which Non-AP MLD Requests Link Change or Reconnection

According to an embodiment, the non-AP MLD may request a link change orreconnection from the AP MLD for efficient data transmission. Forexample, to use an STR capability in data transmission, the non-AP MLDmay request the AP MLD to change or reconnect a connected link.

FIG. 22 illustrates the operations of the AP MLD and the non-AP MLD fora link change or reconnection.

Referring to FIG. 22 , the AP MLD and the non-AP MLD may perform a linkswitching negotiation. STA 2 of the non-AP MLD may transmit a linkswitching request frame to AP 2 of the AP MLD. AP 2 of the AP MLD maytransmit a link switching response frame to STA 2 of the non-AP MLD inresponse to the link switching request frame. The link switching requestframe or the link switching response frame may be transmitted andreceived through a link to be changed, but is not limited thereto. Thelink switching request frame or the link switching response frame may betransmitted and received through various links in addition to the linkto be changed.

The non-AP MLD may request a link change or reconnection by variousmethods.

Hereinafter, three methods for the non-AP MLD to request a link changeor reconnection may be proposed. Specifically, a solicited method, anunsolicited method, and a general method may be sequentially describedas the three methods.

1) Solicited method: Method in which the non-AP MLD requests variouspieces of information of APs included in the AP MLD from the AP MLD andreceives the various pieces of information. For example, the variouspieces of information may include information on a capability, anoperation element, and BSS parameters.

According to an embodiment, a method for the STA to request informationon other APs of the connected AP MLD may be used in various cases inaddition to a case of reconfiguring a link. For example, aftermulti-link setup, for link switching, the STA may request pieces of BSSparameter information on the other APs, and may select a best link basedon the pieces of received information. Alternatively, in a discoveryprocess, the STA may request pieces of BSS load information on therespective APs from the AP MLD, and may select a link to be subjected tolink setup based on the pieces of received information. (Here, it isassumed that the number of APs of the AP MLD is greater than the numberof STAs of the non-AP MLD.)

Accordingly, the AP receiving an information request message maytransmit any information, such as capability information, BSS parameterinformation, critical parameters, and/or operation element information,on all APs in the AP MLD. All of the foregoing examples may be appliedto an embodiment to be described below.

2) Unsolicited method: Method in which the AP transmits various piecesof information without any request for information from the non-AP MLD.The STA may use the pieces of received information in varioussituations. According to an embodiment, a method for the AP of the APMLD to transmit information on other APs without any request forinformation from the STA may be used in various cases in addition to acase of reconfiguring a link. Accordingly, the AP receiving aninformation request message may transmit any information, such ascapability information, BSS parameter information, critical parameters,and/or operation element information, on all APs in the AP MLD. All ofthe foregoing examples may be applied to an embodiment to be describedbelow.

3) General method: Method in which the non-AP MLD requests a link(re)selection without additional information based on informationobtained through a previous beacon frame or the like.

1) Solicited Method

Hereinafter, an embodiment of the solicited method may be described.

According to an embodiment, before a link change or reconnection, thenon-AP MLD may request information for selecting a suitable link fromthe AP MLD. To select a suitable link, the STA may utilize data loadinformation on each AP or capability information on each link (orinformation on other links).

For example, the capability information on each link may be included ina beacon frame to be periodically transmitted.

In another example, the capability information on each link may beoptional information, and may not be included in the beacon frametransmitted every period. Alternatively, to reduce frame overheads, onlyinformation on a link connected to the STA or some associated links maybe received. Alternatively, when a beacon reception period is long dueto a characteristic of the non-AP MLD (e.g., a low-power device), thenon-AP MLD may not receive the capability information on each link forselecting the suitable link.

In the above-described cases, the non-AP MLD may require latestinformation of the capability information on each link and informationon each link of the AP MLD (e.g., BSS parameter information or operationelement information). A link of the capability information on each linkand the information on each link may include not only a link fortransmission and reception but also other links. For example, a field(A-Control field of the 11ax standard) of a QoS data frame, a managementframe, a probe response/request frame, a PS-poll frame, or a null framemay be used to request/transmit the latest information. Alternatively, aseparate new frame may be defined in order to request/transmit thelatest information.

According to an embodiment, to request the latest information of thecapability information on each link and the information on each link ofthe AP MLD, the STA may transmit a request message for requestinginformation necessary for link reselection to the AP. For example, aprobe request frame conventionally defined may be reused for the requestmessage. In another example, a new frame for the request message may bedefined.

According to an embodiment, the STA may designate necessary specificinformation to request the specific information from the AP through therequest message. The specific information that may be designated may bechanged according to circumstances. That is, the STA may request onlyinformation corresponding to a specific link or only informationcorresponding to a specific capability. For example, the informationcorresponding to the specific link may include information on BSSload/parameters of the specific link. The information corresponding tothe capability may include BSS load information on all links or BSS loadinformation on a specific link. In this case, the AP may transmit onlythe information designated by the STA through a response message. Aspecific embodiment related to a request for specific information and aresponse may be described through an embodiment related to thedefinition and operation of an IOM.

In another example, the STA may request all capability information(e.g., including the information on the other links) currently possessedby the AP MLD through the request message.

As in the above examples, an embodiment for transmitting all of theinformation possessed by the AP or an embodiment for transmitting onlythe specific information designated by the STA may be defined/configuredin various manners. For example, the AP may transmit all of theinformation or the designated information based on a separate field orbitmap to indicate (or transmit) only the specific information.

A message for requesting information from the AP MLD may be generallytransmitted through a STA that wants to reconnect, but may also betransmitted to any STA (i.e., other STAs) depending on a situation(channel state or link state).

Upon receiving the request message, the AP MLD may transmit a responsemessage (i.e., an information message) including information (e.g., dataload information on each link and STR capability information betweenlinks) requested by the STA to the non-AP MLD. For example, when aconventional probe request frame is reused for the request message, theAP (or AP MLD) needs to respond using a probe response frame as theresponse message.

The response message may also be generally transmitted through the APhaving received the request message, but may also be transmitted to anyAP (i.e., other APs) by using a multi-link characteristic.

Optionally, the AP MLD may also transmit a “recommend link” elementrecommending a link suitable for the STA through the response messageincluding the foregoing various pieces of information (e.g., the latestinformation required for the link reselection).

The foregoing solicited method may be used for the STA of the non-AP MLDto change or reconnect a link. For example, when the STA of the non-APMLD wants link reselection due to link congestion, the STA of the non-APMLD may request BSS load information and BSS parameter information oneach link of the AP MLD connected through the solicited method. Uponreceiving this request message, the AP may transmit a link andinformation indicated by the STA via a response message.

Hereinafter, the request message and the response message describedabove may be referred to as an information request message and aninformation response message to be distinct from a link change requestmessage and a link change response message.

The STA may reselect a suitable link based on the information includedin the information response message, and may request a link change orreconnection from the AP MLD through a link change request message. Thelink change request message may include information on an AP to whichthe STA is reconnected and information on a link to which the STA isreconnected.

Upon receiving the request message, the AP MLD may transmit a responsemessage of “Accept” when accepting the request. The AP MLD may transmita response message of “Decline” when rejecting the request.

When accepting the request, the AP may perform link (re)setup based on aframe exchange through a reselected link of the AP from a time aftertransmitting the response message. When the request is rejected, the STAmay use the existing connected link as it is.

A specific example of operations of the AP MLD and the non-AP MLDaccording to the solicited method may be described with reference toFIG. 23 .

FIG. 23 illustrates the operations of the AP MLD and the non-AP MLD fora link change or reconnection.

Referring to FIG. 23 , when STA 2 of the non-AP MLD wants to reselect aconnected link, STA 2 may transmit an Info request message to the AP MLDthrough link 2. Upon receiving the Info request message, the AP MLD maytransmit an Info response message including information necessary forlink reselection of the non-AP MLD. STA 2 of the non-AP MLD may transmita link change request message (i.e., a link switching request frame) toAP 2 of the AP MLD based on the information included in the Inforesponse message. Subsequently, STA 2 may receive a link change responsemessage (i.e., a link switching response frame), and may perform link(re)set-up for a link change.

An embodiment of requesting information proposed in the presentspecification may be used/applied even when the STA requests necessaryinformation from the AP. When information included in a frame (e.g., abeacon) received by the STA from the AP is insufficient, the STA mayrequest needed information from the AP. For example, when the APtransmits only information on a connected link without includinginformation on other links or only information on whether theinformation on the other links is updated, the STA may request neededinformation from the AP.

Hereinafter, a new element/field including information for the STA ofthe non-AP MLD to select a suitable link may be proposed.

For example, a “STA ratio per link” (element/field) may be proposed. The“STA ratio per link” may include information on the ratio of STAsconnected per link. A specific example of the “STA ratio per link” maybe described with reference to FIG. 24 .

FIG. 24 illustrates a specific example of a STA ratio per link.

Referring to FIG. 24 , the STA ratio per link (element/field) mayinclude information on the number or ratio of STAs connected per link inthe entire AP MLD.

For example, when a total of 50 STAs are connected to the AP MLD havingthree links, 10 STAs may be connected to link 1 and 20 STAs may beconnected to link 2. The AP MLD may transmit information on STAsconnected per link as information on a value or ratio (%) to the non-APMLD through a STA ratio per link (element/field).

For example, when the information on the STAs connected per link isexpressed as a value, link 1 may be expressed/set as 10 and link 2 maybe expressed/set as 20. Accordingly, the value of STA ratio per link 1may be set to 10. Further, the value of STA ratio per link 2 may be setto 20.

In another example, when the information on the STAs connected per linkis expressed as a ratio, link 1 may be expressed/set as 20 ( 10/50)% andlink 2 may be expressed/set as 40 ( 20/50)%. Accordingly, the value ofSTA ratio per link 1 may be set to 20. Further, the value of STA ratioper link 2 may be set to 40.

The foregoing examples are provided for illustration, and theinformation on the STAs connected per link may be variously set. Inaddition to the foregoing examples, the information on the STAsconnected per link may be set as a relative value.

The STA may identify/obtain the number and ratio of STAs connected perlink based on the information on the STAs connected per link, and mayuse the number and ratio as information for link selection.

According to an embodiment, in addition to the “STA ratio per link”(element/field), various pieces of information/elements/fields may beincluded in the information response message. For example, the followinginformation/element/field may be included in the information responsemessage.

-   -   BSS load information on each AP    -   STR capability information between links    -   TXOP information on each link    -   NAV information on each link    -   Information on recommended link (i.e., “recommend link” element)    -   Information on ratio of STA connected per link (i.e., “STA ratio        per link” element)    -   Etc.

In addition to the foregoing information/element/field, various piecesof information necessary for link selection may be included in theinformation response message and transmitted.

Upon receiving the information illustrated above, the STA may select anAP to which the STA is to change or to be reconnected based on thereceived information, and may then transmit a request message forrequesting link reconnection. Upon receiving the request message, the APMLD may transmit a response message of “Accept” when accepting therequest. The AP MLD may transmit a response message of “Decline” whenrejecting the request.

When the request is accepted, the AP may perform a frame exchangethrough a reselected link with the AP from a time after transmitting theresponse message. When the request is rejected, the STA may use theexisting connected link as it is.

2) Unsolicited Method

Unlike the solicited method in which the non-AP MLD directly requestsadditional information, the unsolicited method enables the AP MLD totransmit additional information to the non-AP MLD through a beacon frameor a separate frame (e.g., a field (A-Control field of the 11axstandard) of a QoS data frame, a management frame, a FILS discoveryframe, an unsolicited probe response frame, a PS-Poll frame, or a nullframe) without a request for the additional information from the non-APMLD. In another example, a new frame may be defined as a frame fortransmitting the additional information to the non-AP MLD.

For example, when a beacon period is fairly long, essential informationrequired for link switching of the non-AP MLD may be insufficient or maynot be up-to-date. Accordingly, the AP may transmit a frame includinglink capability information on the AP MLD to the non-AP MLD.Subsequently, the non-AP STA may obtain latest information on each linkcapability of the AP MLD. The frame may be periodically transmitted ormay be aperiodically transmitted.

For example, when the frame is periodically transmitted, the AP maytransmit the frame at a regular time interval to share latestinformation on the AP. Here, the time interval needs to be shorter thana period of a beacon transmitted by the AP. Further, when a FILSdiscovery frame is used as the frame, the frame may be transmitted every20 us. In another example, a period agreed by the AP and the STA througha capability negotiation may be used. For example, a transmission periodmay be indicated through the value of a “periodic” field and an“interval” field/subfield of an IOM capability element.

In another example, when the frame is aperiodically transmitted, the APmay transmit the frame whenever an event of updating information (acapability, a BSS parameter, and an operation element) on the AP occurs.In a specific example, whenever a link capability of the AP of the APMLD is changed, changed information may be transmitted to the connectedSTA. In this case, the STA may maintain latest information on the linkcapability.

According to the foregoing example, since the non-AP STA does nottransmit a separate request message for obtaining the link capability, aframe exchange overhead is relatively small compared to the solicitedmethod. In addition, since the STA may receive updated informationwhenever main information is updated, the STA may effectively use thereceived information.

A specific example of operations of the AP MLD and the non-AP MLDaccording to the unsolicited method may be described with reference toFIG. 25 .

FIG. 25 illustrates the operations of the AP MLD and the non-AP MLD fora link change or reconnection.

Referring to FIG. 25 , the AP MLD may transmit essential informationrequired for link reselection to the non-AP via a separate frame (e.g.,an Info message) without any request message from the non-AP MLD.

According to an embodiment, unlike FIG. 25 , the AP MLD may transmitpieces of information on a link capability to the STA through a field ofa DL frame (e.g., a QoS data frame) transmitted by the AP MLD to thenon-AP MLD without any request message from the non-AP MLD.

Accordingly, the non-AP MLD may obtain latest link capabilityinformation regardless of a beacon frame period. The non-AP MLD mayselect a suitable link based on the received information in linkswitching. The STA may reselect a suitable link based on the receivedinformation, and may request a link change or reconnection from the APMLD. The request message may include information on an AP to which theSTA is to be reconnected and information on a link to which the STA isto be reconnected. Upon receiving the request message, the AP MLD maytransmit a response message of “Accept” when accepting the request, andmay transmit a response message of “Decline” when rejecting the request.

When the request is accepted, the AP may perform a frame exchangethrough a reselected link with the AP from a time after transmitting theresponse message. When the request is rejected, the STA may use theexisting connected link as it is.

3) General Method

According to the general method, the non-AP MLD may request a linkchange or reconnection based on information currently possessed by thenon-AP MLD without requesting additional information. Here, the usedinformation may include information on the AP MLD and information on thenon-AP MLD (e.g., STR capability information on each link and link state(enabled/disabled) information) included in a previously received beaconor management frame.

Unlike the solicited method, the STA may directly transmit a requestmessage for a link change or reconnection to the AP MLD withoutseparately requesting information from the AP MLD. The request messagemay include information on an AP to which the STA is to be reconnectedand information on a link to which the STA is to be reconnected. Uponreceiving the request message, the AP MLD may transmit a responsemessage of “Accept” when accepting the request, and may transmit aresponse message of “Decline” when rejecting the request.

When the request is accepted, the AP may perform a frame exchangethrough a reselected link with the AP from a time after transmitting theresponse message. When the request is rejected, the STA may use theexisting connected link as it is.

A specific example of operations of the AP MLD and the non-AP MLDaccording to the general method may be described with reference to FIG.26 .

FIG. 26 illustrates the operations of the AP MLD and the non-AP MLD fora link change or reconnection.

Referring to FIG. 26 , STA 2 may want to directly change a link for aguarantee of QoS. When STA 2 has previously received information (e.g.,information received through a beacon frame or management frame) fromthe AP MLD or has already determined a link to which STA 2 wants toreconnect, STA 2 may request a link change or reconnection withoutseparately requesting additional information.

STA 2 may transmit a link switching request frame including STAinformation (e.g., a STA ID) and information on a link to which STA 2wants to change (e.g., a link ID or AP BSS information). Upon receivingthis frame, the AP MLD may transmit a link switching response frame of“Accept” to STA 2 through existing link 2 when accepting the change.Subsequently, STA 2 of the non-AP MLD may perform a link (re)setupprocess, and may then be reconnected to AP 3.

Signaling for Indicating Link Change and Reconnection Method

To indicate the methods proposed above, a mutual agreement process maybe required through a negotiation between the AP MLD and the non-AP MLD.To this end, in the following specification, a signaling method forenabling methods to be proposed may be proposed.

First, to indicate the methods proposed above, a new element may beproposed. Hereinafter, an embodiment of signaling for indicating a linkchange and reconnection method is described, and this embodiment mayalso be applied to an embodiment of signaling for indicating an anchoredlink change and reconnection method.

A signaling process for indicating a link change and reconnection methodmay be performed in multi-link setup or after the multi-link setup. Inaddition, new elements proposed below may be used in the signalingprocess for indicating the link change and reconnection method. Forexample, the elements may be included in an (re)association frame of aconventional standard or a new frame.

Information Obtain Method (IOM) Capability Element

An IOM capability element may include information on whether to enable amethod of obtaining additional information for a multi-link. Forexample, in a process (e.g., a capability negotiation process) in whichthe AP MLD and the non-AP MLD exchange a message to agree on anoperation in a multi-link setup process, an IOM capability value mayexist in an element in the message. The IOM capability value existing inthe element in the message may mean that an IOM capability is supported.

According to an embodiment, when the AP MLD supports the IOM capability,information on other APs may be internally shared with the AP, and theAP may have the information on the other APs. An MLD with which theinformation on the other APs is not shared is not able to support theIOM capability.

According to an embodiment, when the value of the IOM capability elementis set to a first value (e.g., 1), the IOM capability element mayindicate that the IOM is enabled and an indicated function operates.When the value of the IOM capability element is set to a second value(e.g., 0), the IOM capability element may indicate that the IOM isdisabled.

According to an embodiment, the IOM capability element may includevarious fields/elements to indicate various operations. For example, theIOM capability element may include various fields/elements describedbelow. However, a field/element added to the IOM capability element maybe differently configured according to a case in which the AP MLDrequests a link change and a case in which the non-AP MLD requests alink change. Further, at least some of fields/elements added to the IOMcapability element may be omitted. For example, a field/elementincluding information not required to be indicated among thefields/element added to the IOM capability element may be omitted.

Hereinafter, examples of various fields/elements defined/configured toobtain additional information on a multi-link may be described. Variousfields/elements described below may be independently configured, or twoor more fields/elements may be combined and transmitted through variousframes. For example, various fields/elements described below may beincluded in other elements to perform a defining operation. In anotherexample, various fields/elements described below may be used by beingadded to other elements as separate elements or as independent fields.

Method Type (or Method) Field/Element

A method type field/element (hereinafter, a method field/element) mayinclude information on an operation method of the IOM. In other words,the method field/element may indicate the operation method of the IOM.For example, when the non-AP MLD enables the IOM to obtain informationfrom the AP, the non-AP MLD may select and indicate a method to be usedfrom among the methods proposed above (e.g., the solicited method, theunsolicited method, and the general method).

For example, the solicited method may be indicated/used based on thevalue of the method field/element being a first value (e.g., 0). Theunsolicited method may be indicated/used based on the value of themethod field/element being a second value (e.g., 1). The general methodmay be indicated/used based on the value of the method field/elementbeing a third value (e.g., 2). Both the solicited method and theunsolicited method may be indicated/used based on the value of themethod field/element being a fourth value (e.g., 3).

In another example, one bit may be used for the method field/element. Inthis case, the solicited method may be indicated/used based on the valueof the method field/element being a first value (e.g., 0). Theunsolicited method may be indicated/used based on the value of themethod field/element being a second value (e.g., 1).

In another example, two bits may be used for the method field/element.In this case, the methods may be indicated to be used independently orin combination.

Link Range Field/Element

When the non-AP MLD requests information from the AP MLD, the non-AP MLDmay indicate a requested link range through a link range field/element.The link range field/element may include information on whether the STAwants to request information on all links in the AP MLD or informationon some links in the AP MLD.

For example, when the value of the link range field/element is a firstvalue (e.g., 0), the link range field/element may indicate thatinformation on all links in the AP MLD is requested. When the value ofthe link range field/element is a second value (e.g., 1), the link rangefield/element may indicate that information on some links in the AP MLDis requested.

Here, when the value of the link range field/element is the first value(e.g., 0), which is a request for all links in the AP MLD, separate linkindicator information (e.g. a “link condition” field) is not required.When the value of the link range field/element is the second value(e.g., 1), which is a request for the information on some links in theAP MLD, link indicator information is required.

Info Range Field/Element

An info range field may be used to indicate the range of informationwhen the non-AP MLD requests the information.

For example, when the value of the info range field is a first value(e.g., 0), the info range field may indicate that only partialinformation possessed by the AP is provided. When the value of the inforange field is a second value (e.g., 1), the info range field mayindicate that complete information (or all information) possessed by theAP is provided.

According to an embodiment, the info range field may be defined toindicate a request for all or partial of the information (element)possessed by the AP, but the STA may request more detailed informationthrough an additional subfield. For example, a subfield for indicatingthe range of information to be provided (e.g., all information orpartial information) may be included in the info range field. Forexample, the subfield for indicating the range of the information to beprovided may be defined/configured as an all/partial subfield.

According to an embodiment, a subfield for indicating whether to receiveall information or only changed information among all the informationmay be newly proposed. In other words, the newly proposed subfield mayindicate whether to receive all information or only changed informationamong all the information.

For example, the subfield for indicating whether to receive allinformation or only changed information among all the information may bedefined/configured as an only updated subfield.

When the STA wants to receive only changed information, the value of theonly updated subfield may be set to 1. In other words, when the STAwants to receive only changed information, the STA may set the value ofthe only updated subfield to 1. For example, according to the solicitedmethod, when the value of the only updated subfield is set to 1, the AP(or AP MLD) may transmit only changed information (i.e., updatedinformation) among requested information when the STA requests theinformation. In another example, according to the unsolicited method,when the value of the only updated subfield is set to 1, only changedinformation in an information range set by the STA may be notified bythe AP.

Although the only updated subfield in the info range field is proposedto receive only changed information in the above example, the presentspecification is not limited thereto. A separate field or element may bedefined/configured to receive only changed information.

According to the foregoing embodiment, the range of information that theSTA is allowed to request may be set to updated information or allinformation. In this case, the STA that does not want high frameoverhead may request reception of only changed information. Accordingly,it is possible to reduce overhead.

Link Condition Field/Element

A link condition field may be used to indicate a requested specificlink. In other words, the link condition field may include informationon the requested specific link. The link condition field may be usedwhen the STA wants to receive only specific link information from theAP.

The link condition field may be indicated by a link identifier (e.g., alink ID or a BSS ID). In other words, the link condition field mayinclude information on the link identifier (e.g., the link ID or the BSSID). In other words, the link identifier may be used to specify a linkfor obtaining information.

For example, when the STA connected to link 1 wants to request onlyinformation on link 2 and link 3 from the AP, the STA may request theinformation on link 2 and link 3 from the AP by indicating link 2 andlink 3 in a link condition field. For example, when the value of theforegoing info range field is 1, all information corresponding to link 2and link 3 may be transmitted. In another example, when the value of theinfo range field is 0, partial information on link 2 and link 3designated by the STA may be transmitted. According to an embodiment,partial information designated by the STA may be determined through thefollowing Info condition field.

According to an embodiment, when the link condition field has no valueor has a value of 0, the AP may determine that there is no linkcondition. Accordingly, the AP may provide/transmit information on alllinks to the STA.

Info Condition Field/Element

An info condition field may be used to indicate a requested specificinformation type. In other words, the info condition field may be usedwhen the STA wants to receive only specific information from the AP.

For example, the info condition field may be used only when the inforange field is set to 0. In another example, the info condition fieldmay be used by the STA to indicate specific information even when thereis no info range field.

For example, in the info condition field, information (e.g., a BSS loador an STR capability) specifiable by the STA may be indicated by abitmap. For example, the type of information provided by the AP and anindication method or order thereof in bits may be variously set.

According to an embodiment, the info condition field may be usedtogether with the foregoing link condition field. According to anembodiment, the info condition field may transmit requested informationof various conditions to the STA (or AP) based on a combination ofvarious fields/elements.

According to an embodiment, a field/element defined/configured to obtainadditional information on a multi-link is not limited to the foregoingfield/elements, and various fields/elements may be further configured.

Therefore, the MLD (AP MLD or non-AP MLD) may indicate an IOM capabilitythrough a negotiation between the AP MLD and the non-AP MLD using atleast one of the elements/fields described above in the multi-link setupprocess. In addition, the MLD may update the agreement between the MLDsthrough a separate message exchange after the multi-link setup iscompleted.

According to an embodiment, when the IOM capability is enabled, the APMLD and the non-AP MLD may operate based on an embodiment for a linkchange and reconnection.

Hereinafter, an example of operations of the AP MLD and the non-AP MLDwhen the IOM capability is enabled may be described. For example, thenon-AP MLD may request additional information for a multi-link bytransmitting the foregoing fields/elements to the AP MLD. The non-AP MLDmay transmit an IOM capability element including the foregoingfields/elements to the AP MLD. The foregoing fields/elements beingincluded in the IOM capability element is for illustration, and thefields/elements may also be transmitted as independent fields/elements.

For example, in the multi-link setup process, the non-AP MLD maytransmit an IOM capability element including “Method field=0” and “Inforange field=1” to the AP MLD, and may agree thereon with the AP MLD. Inthis case, after multi-link setup, the non-AP MLD operates according tothe solicited method, and may request information for the multi-link(e.g., information on other APs) including all information included in abeacon when request information. Accordingly, the AP MLD mayprovide/transmit information on a link via a response message only whenreceiving a request message from the STA. When receiving the requestmessage, the AP MLD may transmit the response message includinginformation on all links in the AP MLD to the STA. The information onall links in the AP MLD may include all information included in thebeacon.

In another example, the non-AP MLD may transmit an IOM capabilityelement including “Method field=1”, “Info range field=0”, “Linkrange=Link id 2”, and “Info condition field=(value indicating BSS loadthrough bitmap) to the AP MLD, and may agree thereon with the AP MLD. Inthis case, after multi-link setup, the non-AP MLD may operate accordingto the unsolicited method. Accordingly, the AP may transmit BSS loadinformation of link 2 to the STA through a separate message withoutreceiving a separate request message.

According to an embodiment, the AP MLD and the non-AP MLD may enable theproposed IOM through the signaling method proposed in the presentspecification during the multi-link setup process or after themulti-link setup. In addition, the AP MLD and the non-AP MLD may limitthe range and type of requested information through various field valuesin the IOM capability element.

According to an embodiment, an IOM operation may be performed after anaccurate operation negotiation between the MLDs through the foregoingIOM signaling method, but the IOM operation may also be performed byimplementation by the MLDs without a separate signaling process. Thatis, the operation may be performed by implementation by the AP MLD or byimplementation by the non-AP MLD without a negotiation between the APMLD and the non-AP MLD.

The AP MLD and the non-AP MLD may operate based on the foregoingembodiments. However, when the MLDs perform the IOM operation without aseparate signaling exchange, the following constraints may occur.

1) Constraints on the solicited method: When information sharing is notsupported between APs of the AP MLD, it is impossible to respond whenthe STA requests information on another link.

2) Constraints on the unsolicited method: The AP may provide a separatemessage by autonomously determining a STA that needs additional linkinformation (e.g., a beacon period). Accordingly, the STA cannot predictin advance whether the STA will receive this information.

When the MLDs implement the IOM without a separate signaling method, anoperation process may be simplified, whereas the foregoing constraintsmay occur.

Embodiment for Anchored Link Change and Reconnection

According to an embodiment, the AP MLD may support an anchored link.When the AP MLD supports the anchored link, there are additionalconsiderations to be taken into account in the foregoing embodiment forthe link change and reconnection.

The AP MLD may support one or more anchored links, and may provideinformation on one or more anchored links to the non-AP MLD throughanchored link list information/element. The non-AP MLD may select anduse one or more links in the anchored link list as anchored linksthereof. Links other than those selected as the anchored links mayoperate as non-anchored links.

An anchored link and a non-anchored link have a trade-off relationshipin terms of power consumption and data load. That is, when the non-APMLD uses one anchored link, power consumption may be reduced, whereasQoS of data (especially, data on a beacon and a management frame)transmission may not be guaranteed. However, when a plurality ofanchored links is used, QoS of data transmission may be guaranteed,whereas the amount of power reduction may be reduced.

Therefore, the non-AP MLD needs to be able to dynamically requestreselection of an anchored link for an efficient data exchange.Hereinafter, an embodiment in which the non-AP MLD dynamically requestsan anchored link change/reselection may be proposed.

First, an MLD structure supporting an anchored link may be describedwith reference to FIG. 27 .

FIG. 27 illustrates an example of an MLD structure supporting ananchored link.

Referring to FIG. 27 , an AP MLD may use two links (i.e., AP 1 and AP 4)among five links as anchored links. A non-AP MLD may use one anchoredlink by selecting link 1 among the two links used as the anchored links.The remaining links of the non-AP MLD may be connected to non-anchoredlinks (link 2 and link 3). That is, the non-AP MLD needs to alwaysmonitor link 1 to receive a beacon and a management frame.

According to an embodiment, STA 1 may make a request to change apreviously used anchored link from the anchored link of AP 1 to theanchored link of AP 4 for load balancing or the like. To change theanchored link, the foregoing embodiment related to link switching may beapplied.

However, some limited links among links supported by the AP MLD aresupported as anchored links. Accordingly, the AP MLD may have a separateanchored link list. The non-AP MLD (or STA) needs to select one linkincluded in the anchored link list and to request a change orreconnection thereto. In addition, the non-AP MLD needs to have at leastone anchored link, and thus needs to request an anchored link change inconsideration of this aspect when requesting a link change orreconnection.

For the foregoing embodiment, the AP MLD needs to additionally provide“Anchored Link List” information to the non-AP MLD. This information maybe included in a frame in the form of a new element or field. The term“Anchored Link List” is for illustration, and may be set/expressedvariously.

-   -   “Anchored link list” (element/field): List information of        anchored links currently supported by the AP MLD. For example,        the list information of the anchored links currently supported        by the AP MLD may be indicated/set by one or more link IDs or AP        BSS values. The non-AP MLD needs to be connected to at least one        anchored link among the links included in the list.

The foregoing information (e.g., “Anchored Link List” (element/field))may be included and transmitted in an existing beacon or managementframe, or may be included and transmitted in an info response message tothe non-AP MLD according to the solicited method.

Accordingly, when the non-AP MLD requests a change of an anchored linkused by the non-AP MLD, the non-AP MLD needs to know currently supportedanchored link list information in advance. When the non-AP MLD does notknow the anchored link list information or wants to obtain the latestinformation, the non-AP MLD may obtain the information from the AP MLDaccording to the solicited method.

The STA may request a change or reconnection to only one link in theanchored link list based on the anchored link list information. When theSTA requests a change or reconnection to another link not included inthe list, the AP MLD may transmit a rejection message to the STA.

When changing or reconnecting an anchored link, there is an additionalconsideration to be taken into account in addition to the existing linkchange method. There are two general cases where the STA of the non-APMLD changes an anchored link.

In a first case, the STA already connected to the anchored link changesto another anchored link of the AP MLD for load balancing or the like(change of AP for an anchored link). In a second case, the STA connectedto the anchored link is disabled due to a power state or the like, andthus another STA of the non-AP MLD is reconnected to the anchored link(STA change for an anchored link).

The first case may operate similarly/equally to the foregoing embodimentfor the link change and reconnection. Here, when the STA reselects alink, the STA needs to select a link in the anchored link list supportedby the AP MLD. When another link is selected, the AP MLD may transmit arejection response message.

The second case requires an additional consideration. An example of thesecond case may be described with reference to FIG. 28 .

FIG. 28 illustrates an example of a situation in which an anchored linkchange or reconnection is required.

Referring to FIG. 28 , the STA of the non-AP MLD may have a state of STA1 disabled for various reasons (e.g., power-off). Here, since both STA 2and STA 3 are currently connected to a non-anchored link, one of theSTAs needs to be reconnected to an anchored link.

As shown in FIG. 28 , when the non-AP MLD needs to reconnect to theanchored link, the non-AP MLD may attempt to reconnect one of STA 2 andSTA 3 to the anchored link.

For example, when the non-AP MLD has information on the anchored linklist supported by the AP MLD, the non-AP MLD may select a suitable linkto request a link change.

In another example, when the non-AP MLD does not have the information onthe anchored link list supported by the AP MLD, the non-AP MLD mayobtain the information from the AP MLD through an info request, and maythen select a suitable link to request a link change.

A specific example of operations of the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 29 .

FIG. 29 illustrates the operations of the AP MLD and the non-AP MLD foran anchored link change or reconnection.

Referring to FIG. 29 , when STA 1 connected to the anchored link isdisabled, the non-AP MLD needs a new connection to the anchored link.Here, the non-AP MLD may disconnect STA 3 from the previously connectednon-anchored link to AP 3, and may attempt to reconnect STA 3 to theanchored link.

For example, STA 3 may attempt to connect to AP 1 used as the existinganchored link. In another example, STA 3 may attempt to connect to newAP 4 based on various pieces of information.

A process of selecting a new anchored link may be performed in the samemanner as/similarly to the foregoing embodiment for the link change orreconnection. For example, STA 3 may request a reconnection by selectingan anchored link recommended by the AP or directly selecting an anchoredlink by STA 3. After the reconnection to the anchored link is completed,the link of STA 3 may operate as an anchored link.

Element/Field Including Information on Anchored Link

According to an embodiment, when information on an anchored linksupported by the AP MLD is changed or the STA directly requestsinformation on an anchored link, the AP MLD may transmit the information(i.e., the changed information on the anchored link or the informationon the anchored link requested by the STA) to the non-AP MLD.

For example, the information may be information related to an anchoredlink currently used, and may be included and transmitted in a beaconframe or may be included and transmitted in a separate management frame.

The information on the anchored link may include the foregoing “anchoredlink list” element indicating an anchored link supported by the AP MLDand information on whether an anchored link is used for each STA of thenon-AP MLD.

Hereinafter, new elements including the information on the anchored linkillustrated above may be proposed. Newly proposed elements may beconfigured/set as follows.

1)“Anchored link indication” element (or field): The “anchored linkindication” element may include information on whether an anchored linkis used for all STAs connected to the AP MLD. That is, the “anchoredlink indication” element may be an element/field indicating whether ananchored link is used for each link or each STA of the non-AP MLD.

2) “STA ratio per anchored link” element (or field): The “STA ratio peranchored link” element may include information on the ratio or number ofSTAs connected for each anchored link. Here, only a STA using a link asan anchored link may be considered. In other words, even though the APMLD supports a first link as an anchored link, a STA using the firstlink as a non-anchored link may not be included in STAs connected foreach anchored link.

According to an embodiment, the elements may be included as additionalinformation in a frame, if necessary, in any process of the foregoingembodiment for the anchored link change or reconnection.

A specific example of the elements may be described with reference toFIG. 30 and FIG. 31 .

FIG. 30 and FIG. 31 illustrate specific examples of an element for ananchored link reconnection.

Referring to FIG. 30 and FIG. 31 , information on an anchored link maybe transmitted through an anchored link list element (or field), ananchored link indication element (or field), and/or a STA ratio peranchored link element (or field). In other words, an element for ananchored link reconnection may include the anchored link list element(or field), the anchored link indication element (or field), and/or theSTA ratio per anchored link element (or field).

According to an embodiment, the anchored link list element may includeinformation on a list of links currently supported by the AP MLD asdescribed above. For example, lithe information on the list of linkscurrently supported by AP MLD may be indicated based on a link ID or APBSS information. In other words, the list of links currently supportedby AP MLD may be configured/set based on the link ID or the AP BSSinformation.

According to an embodiment, the anchored link indication element mayinclude information on whether an anchored link is used for each STA ofthe non-AP MLD. For example, the information on whether the anchoredlink is used for each STA of the non-AP MLD may be indicated/specifiedfor each link through an indication bitmap. (i.e., FIG. 28 ). In anotherexample, whether an anchored link is used for all STAs may beindicated/specified through one bitmap. (i.e., FIG. 29 ).

For example, when the information on whether the anchored link is usedis indicated through an indication bitmap according to a link ID, theSTA may identify a current anchored link based on the value of theanchored link list element. Accordingly, the STA may identify the ratioof STAs connected to each anchored link. Here, an indication bitmapfield for a non-anchored link may be omitted to reduce overhead.

When the value of one bit in the bitmap is 1, the one bit may mean thata link currently connected to the STA is an anchored link. When thevalue of one bit in the bitmap is 0, the one bit may mean that the linkcurrently connected to the STA is a non-anchored link. An embodiment ofusing a bitmap to indicate whether an anchored link is connected foreach STA is for illustration, and information on whether the anchoredlink is connected for each STA may be transmitted through variousembodiments.

According to an embodiment, the ratios of STAs for all links supportedby the AP MLD may be transmitted. According to an embodiment, the STAratio per anchored link element may include information on the ratio ornumber of STAs using each anchored link as an actual anchored link. Forexample, this information may be indicated only for an anchored linkindicated/specified in the anchored link list element, thereby reducingoverhead.

An example in which the value of the STA ratio per anchored link elementis set may be described below.

For example, the AP MLD may include five APs (i.e., AP 1 to AP 5), andAP 1 may be connected to STAs through link 1. AP 2 may be connected toSTAs through link 2. AP 3 may be connected to STAs through link 3. AP 4may be connected to STAs through link 4. AP 5 may be connected to STAsthrough link 5.

The AP MLD may support two links among the five links (i.e., link 1 tolink 5) as anchored links. Link 1 and link 4 may be supported/used asanchored links.

A total of 10 STAs are connected to link 1 (or AP 1), and seven STAs mayuse link 1 as an anchored link, which may be expressed/represented as70% in ratio, and may be expressed/represented as 7 in value.

A total of 20 STAs are connected to link 4 (or AP 4), and five STAs mayuse link 4 as an anchored link, which may be expressed/represented as25% in ratio, and may be expressed/represented as 5 in value.

The STA ratio per anchored link element may be transmitted together withthe foregoing STA ratio per link element information, thus transmittingmore accurate information to the STA. In general, since an anchored linkmay have more data traffic than a non-anchored link, the STA ratio peranchored link element may be used as useful information for a STAreselecting an anchored link.

The non-AP MLD may identify whether a link to which the non-AP MLD isconnected is an anchored link, the ratio of STAs connected to eachanchored link, and the ratio of STAs actually using an anchored linkbased on the foregoing pieces of information (or elements).

Additionally, when the AP MLD transmits information on other links, thatis, all links, through the foregoing elements, the STA may identify theratios of STAs connected to all anchors links of the AP MLD and theratios of STAs actually using all anchored links based on one frame.Accordingly, the foregoing pieces of information (or elements) may beused when reselecting an anchored link to be used by the STA.

Therefore, according to the embodiment for the anchored link change orreselection, it is possible to change or reconnect to a more suitableanchored link by using not only various pieces of link information(e.g., the BSS load information for each AP or the STR capabilityinformation for each link) used in the embodiment for the link change orreselection but also the foregoing pieces of information on the anchoredlink (e.g., the anchored link list information, the informationindication whether the anchored link is used for each STA, or theinformation on the ratio of STAs actually using each anchored link).

FIG. 32 is a flowchart illustrating the operation of a multi-linkdevice.

Referring to FIG. 32 , in operation S3210, the multi-link device mayreceive a PPDU through a first link among a plurality of links. Forexample, the plurality of links may be included in 2.4 GHz, 5 GHz, and 6GHz bands.

For example, the multi-link device may be connected to an AP multi-linkdevice through a plurality of links including the first link and asecond link. The multi-link device may include a plurality of STAsrelating to the plurality of links. The multi-link device may include afirst STA and a second STA.

For example, the first STA among the plurality of STAs may be connectedto the first link. In other words, the first STA may operate in thefirst link. Further, the first STA may be connected to a first AP of theAP multi-link device through the first link.

For example, the second STA among the plurality of STAs may be connectedto the second link. In other words, the second STA may operate in thesecond link. Further, the second STA may be connected to a second AP ofthe AP multi-link device through the second link.

According to an embodiment, the PPDU may include a first informationfield related to the second link that is distinct from the first linkamong the plurality of links. The first information field may includeinformation on the second link.

For example, the first information field related to the second link mayinclude a second information field related to a link identifier of thesecond link and a third information field related to whether completeelement information for the second link is included in the PPDU.

The second information field may include four bits. The secondinformation field may include link identifier (ID) information on thesecond link. The link identifier of the second link may be set to fourbits. The second information field may include a link ID field.

The third information field may include one bit. The third informationfield may be set to a first value. For example, the multi-link devicemay identify that the complete element information for the second linkis included in the PPDU based on the third information field being setto the first value (e.g., 1). In another example, the multi-link devicemay identify that partial element information on the second link isincluded in the PPDU based on that the third information field being setto a second value (e.g., 0). The third information field may include acomplete profile field.

According to an embodiment, the complete element information for thesecond link may be configured based on the type of the PPDU. In otherwords, the complete element information included in the PPDU may bechanged according to the type of the PPDU. For example, pieces ofelement information that may be included in a probe request frame may beset/defined. In another example, pieces of element information that maybe included in an (re)association response frame may be set/defined.Accordingly, when the PPDU is a probe request frame, the multi-linkdevice may identify whether all of the pieces of element informationthat may be included in the probe request frame are included in the PPDUbased on the third information field.

According to an embodiment, the PPDU may further include a fourthinformation field related to a third link among the plurality of links.The fourth information field may include a fifth information fieldrelated to a link identifier of the third link and a sixth informationfield related to whether the complete element information for the thirdlink is included in the PPDU.

According to an embodiment, the multi-link device may transmit a secondPPDU for requesting the complete element information for the secondlink. The multi-link device may receive the PPDU including the firstinformation field based on the second PPDU.

In operation S3220, the multi-link device may obtain the completeelement information for the second link based on the second informationfield and the third information field.

According to an embodiment, the first link may operate as an anchoredlink. The second link may operate as a non-anchored link.

For example, the multi-link device may change a link operating as theanchored link from the first link to the second link based on thecomplete element information for the second link. In one example, themulti-link device may identify traffic load information on the secondlink. The multi-link device may transmit a frame (or PPDU) for changingthe link serving as the anchored link from the first link to the secondlink based on the traffic load information on the second link.

FIG. 33 is a flowchart illustrating the operation of an AP multi-linkdevice.

Referring to FIG. 33 , in operation S3310, the AP multi-link device maygenerate a PPDU. For example, a plurality of links may be included in2.4 GHz, 5 GHz, and 6 GHz bands.

For example, the AP multi-link device may be connected to a multi-linkdevice through the plurality of links including a first link and asecond link. The AP multi-link device may include a plurality of APsrelating to the plurality of links. The AP multi-link device may includea first AP and a second AP.

For example, the first AP among the plurality of APs may be connected tothe first link. In other words, the first AP may operate in the firstlink. Further, the first AP may be connected to a first STA of themulti-link device through the first link.

For example, the second AP among the plurality of APs may be connectedto the second link. In other words, the second AP may operate in thesecond link. Further, the second AP may be connected to a second STA ofthe multi-link device through the second link.

According to an embodiment, the PPDU may include a first informationfield related to the second link that is distinct from the first linkamong the plurality of links. The first information field may includeinformation on the second link.

For example, the first information field related to the second link mayinclude a second information field related to a link identifier of thesecond link and a third information field related to whether completeelement information for the second link is included in the PPDU.

The second information field may include four bits. The secondinformation field may include link identifier (ID) information on thesecond link. The link identifier of the second link may be set to fourbits. The second information field may include a link ID field.

The third information field may include one bit. The third informationfield may be set to a first value. For example, the AP multi-link devicemay set the third information field to the first value (e.g., 1) toindicate that the complete element information for the second link isincluded in the PPDU. In another example, the AP multi-link device mayset the third information field to a second value (e.g., 0) to indicatethat partial element information on the second link is included in thePPDU. The third information field may include a complete profile field.

According to an embodiment, the complete element information for thesecond link may be configured based on the type of the PPDU. In otherwords, the complete element information included in the PPDU may bechanged according to the type of the PPDU. For example, pieces ofelement information that may be included in a probe request frame may beset/defined. In another example, pieces of element information that maybe included in an (re)association response frame may be set/defined.Accordingly, when the PPDU is a probe request frame, the AP multi-linkdevice may transmit the PPDU including the third information fieldindicating whether all of the pieces of element information that may beincluded in the probe request frame are included in the PPDU.

According to an embodiment, the PPDU may further include a fourthinformation field related to a third link among the plurality of links.The fourth information field may include a fifth information fieldrelated to a link identifier of the third link and a sixth informationfield related to whether the complete element information for the thirdlink is included in the PPDU.

According to an embodiment, the AP multi-link device may receive asecond PPDU for requesting the complete element information for thesecond link. The AP multi-link device may transmit the PPDU includingthe first information field based on the second PPDU.

In operation 3320, the AP multi-link device may transmit the PPDUthrough the first link among the plurality of links. For example, thefirst link may operate as an anchored link. The second link may operateas a non-anchored link. The AP multi-link device may transmit the PPDUincluding the information on the second link through the first link asthe anchored link.

The foregoing technical features of the present specification may beapplied to various devices and methods. For example, the foregoingtechnical features of the present specification may beperformed/supported through the apparatus of FIG. 1 and/or FIG. 14 . Forexample, the foregoing technical features of the present specificationmay be applied to only part of FIG. 1 and/or FIG. 14 . For example, theforegoing technical features of the present specification may beimplemented based on the processing chips 114 and 124 of FIG. 1 , may beimplemented based on the processors 111 and 121 and the memories 112 and122 of FIG. 1 , or may be implemented based on the processor 610 and thememory 620 of FIG. 14 . For example, an apparatus of the presentspecification may include a processor and a memory connected to theprocessor, wherein the processor may be configured to: generate a PPDU,the PPDU including a first information field related to a second linkdistinct from a first link among a plurality of links, and the firstinformation field related to the second link including a secondinformation field related to a link identifier of the second link and athird information field related to whether complete element informationfor the second link is included in the PPDU; and transmit the PPDUthrough the first link among the plurality of links.

The technical features of the present specification may be implementedbased on a computer-readable medium (CRM). For example, the CRM proposedaccording to the present specification may be encoded with at least onecomputer program including instructions. When executed by at least oneprocessor, the instructions may cause the at least one processor toperform operations including: receiving a physical layer protocol dataunit (PPDU) through a first link among the plurality of links, the PPDUincluding a first information field related to a second link distinctfrom the first link among the plurality of links, and the firstinformation field related to the second link including a secondinformation field related to a link identifier of the second link and athird information field related to whether complete element informationfor the second link is included in the PPDU; and obtaining the completeelement information for the second link based on the second informationfield and the third information field. The instructions stored in theCRM of the present specification may be executed by at least oneprocessor. The least one processor related to the CRM of the presentspecification may be the processors 111 and 121 or the processing chips114 and 124 of FIG. 1 or may be the processor 610 of FIG. 14 . The CRMof the present specification may be the memories 112 and 122 of FIG. 1 ,may be the memory 620 of FIG. 14 , or may be a separate externalmemory/storage medium/disk.

The foregoing technical features of this specification are applicable tovarious applications or business models. For example, the foregoingtechnical features may be applied for wireless communication of a devicesupporting artificial intelligence (AI).

Artificial intelligence refers to a field of study on artificialintelligence or methodologies for creating artificial intelligence, andmachine learning refers to a field of study on methodologies fordefining and solving various issues in the area of artificialintelligence. Machine learning is also defined as an algorithm forimproving the performance of an operation through steady experiences ofthe operation.

An artificial neural network (ANN) is a model used in machine learningand may refer to an overall problem-solving model that includesartificial neurons (nodes) forming a network by combining synapses. Theartificial neural network may be defined by a pattern of connectionbetween neurons of different layers, a learning process of updating amodel parameter, and an activation function generating an output value.

The artificial neural network may include an input layer, an outputlayer, and optionally one or more hidden layers. Each layer includes oneor more neurons, and the artificial neural network may include synapsesthat connect neurons. In the artificial neural network, each neuron mayoutput a function value of an activation function of input signals inputthrough a synapse, weights, and deviations.

A model parameter refers to a parameter determined through learning andincludes a weight of synapse connection and a deviation of a neuron. Ahyper-parameter refers to a parameter to be set before learning in amachine learning algorithm and includes a learning rate, the number ofiterations, a mini-batch size, and an initialization function.

Learning an artificial neural network may be intended to determine amodel parameter for minimizing a loss function. The loss function may beused as an index for determining an optimal model parameter in a processof learning the artificial neural network.

Machine learning may be classified into supervised learning,unsupervised learning, and reinforcement learning.

Supervised learning refers to a method of training an artificial neuralnetwork with a label given for training data, wherein the label mayindicate a correct answer (or result value) that the artificial neuralnetwork needs to infer when the training data is input to the artificialneural network. Unsupervised learning may refer to a method of trainingan artificial neural network without a label given for training data.Reinforcement learning may refer to a training method for training anagent defined in an environment to choose an action or a sequence ofactions to maximize a cumulative reward in each state.

Machine learning implemented with a deep neural network (DNN) includinga plurality of hidden layers among artificial neural networks isreferred to as deep learning, and deep learning is part of machinelearning. Hereinafter, machine learning is construed as including deeplearning.

The foregoing technical features may be applied to wirelesscommunication of a robot.

Robots may refer to machinery that automatically process or operate agiven task with own ability thereof. In particular, a robot having afunction of recognizing an environment and autonomously making ajudgment to perform an operation may be referred to as an intelligentrobot.

Robots may be classified into industrial, medical, household, militaryrobots and the like according uses or fields. A robot may include anactuator or a driver including a motor to perform various physicaloperations, such as moving a robot joint. In addition, a movable robotmay include a wheel, a brake, a propeller, and the like in a driver torun on the ground or fly in the air through the driver.

The foregoing technical features may be applied to a device supportingextended reality.

Extended reality collectively refers to virtual reality (VR), augmentedreality (AR), and mixed reality (MR). VR technology is a computergraphic technology of providing a real-world object and background onlyin a CG image, AR technology is a computer graphic technology ofproviding a virtual CG image on a real object image, and MR technologyis a computer graphic technology of providing virtual objects mixed andcombined with the real world.

MR technology is similar to AR technology in that a real object and avirtual object are displayed together. However, a virtual object is usedas a supplement to a real object in AR technology, whereas a virtualobject and a real object are used as equal statuses in MR technology.

XR technology may be applied to a head-mount display (HMD), a head-updisplay (HUD), a mobile phone, a tablet PC, a laptop computer, a desktopcomputer, a TV, digital signage, and the like. A device to which XRtechnology is applied may be referred to as an XR device.

The claims recited in the present specification may be combined in avariety of ways. For example, the technical features of the methodclaims of the present specification may be combined to be implemented asa device, and the technical features of the device claims of the presentspecification may be combined to be implemented by a method. Inaddition, the technical characteristics of the method claim of thepresent specification and the technical characteristics of the deviceclaim may be combined to be implemented as a device, and the technicalcharacteristics of the method claim of the present specification and thetechnical characteristics of the device claim may be combined to beimplemented by a method.

1. A method performed by a multi-link device (MLD) operating in aplurality of links in a wireless local area network system, the methodcomprising: receiving a physical layer protocol data unit (PPDU) througha first link among the plurality of links, wherein the PPDU includes afirst information field related to a second link distinct from the firstlink among the plurality of links, and wherein the first informationfield related to the second link includes a second information fieldrelated to a link identifier of the second link and a third informationfield related to whether complete element information for the secondlink or partial element information for the second link is included inthe PPDU, and the third information field has a length of one bit; andobtaining the complete element information for the second link based onthe second information field and the third information field.
 2. Themethod of claim 1, wherein the second information field comprises fourbits.
 3. The method of claim 1, wherein the third information field hasa value of one for the complete element information, the thirdinformation field has a value of zero for the partial elementinformation.
 4. The method of claim 1, wherein the complete elementinformation for the second link is set based on whether the PPDU is aprobe request frame or a (re)association response frame.
 5. The methodof claim 1, wherein the first link operates as an anchored link, and thesecond link operates as a non-anchored link.
 6. The method of claim 5,further comprising: changing a link operating as the anchored link fromthe first link to the second link based on the complete elementinformation for the second link.
 7. The method of claim 1, furthercomprising: transmitting a second PPDU for requesting the completeelement information for the second link.
 8. The method of claim 1,wherein the PPDU further comprises a fourth information field related toa third link among the plurality of links.
 9. The method of claim 1,wherein the plurality of links is included in one of 2.4 GHz, 5 GHz, and6 GHz bands.
 10. (canceled)
 11. A method performed by an access point(AP) multi-link device operating in a plurality of links in a wirelesslocal area network system, the method comprising: generating a physicallayer protocol data unit (PPDU), wherein the PPDU includes a firstinformation field related to a second link distinct from a first linkamong the plurality of links, and wherein the first information fieldrelated to the second link includes a second information field relatedto a link identifier of the second link and a third information fieldrelated to whether complete element information for the second link orpartial element information for the second link is included in the PPDU,and the third information field has a length of one bit; andtransmitting the PPDU through the first link among the plurality oflinks.
 12. A multi-link device (MLD) used in a wireless local areanetwork system and operating in a plurality of links, the MLDcomprising: a transceiver to transmit and receive a radio signal; and aprocessor connected to the transceiver, wherein the processor isconfigured to: receive a physical layer protocol data unit (PPDU)through a first link among the plurality of links, wherein the PPDUincludes a first information field related to a second link distinctfrom the first link among the plurality of links, and wherein the firstinformation field related to the second link includes a secondinformation field related to a link identifier of the second link and athird information field related to whether complete element informationfor the second link or partial element information for the second linkis included in the PPDU, and the third information field has a length ofone bit; and obtain the complete element information for the second linkbased on the second information field and the third information field.13. The MLD of claim 12, wherein the second information field comprisesfour bits.
 14. The MLD of claim 12, wherein the third information fieldhas a value of one for the complete element information, the thirdinformation field has a value of zero for the partial elementinformation.
 15. The MLD of claim 12, wherein the complete elementinformation for the second link is set based on whether the PPDU is aprobe request frame or a (re)association response frame.
 16. The MLD ofclaim 12, wherein the first link operates as an anchored link, and thesecond link operates as a non-anchored link.
 17. The MLD of claim 12,wherein the processor is further configured to transmit a second PPDUfor requesting the complete element information for the second link. 18.An access point (AP) multi-link device (MLD) used in wireless local areanetwork system and operating in a plurality of links, the AP MLDcomprising: a transceiver to transmit and receive a radio signal; and aprocessor connected to the transceiver, wherein the processor isconfigured to: generate a PPDU physical layer protocol data unit (PPDU),wherein the includes a first information field related to a second linkdistinct from a first link among the plurality of links, and wherein thefirst information field related to the second link includes a secondinformation field related to a link identifier of the second link and athird information field related to whether complete element informationfor the second link or partial element information for the second linkis included in the PPDU, and the third information field has a length ofone bit; and transmit the PPDU through the first link among theplurality of links.
 19. (canceled)
 20. (canceled)